[[pp. 38702-38752]] National Ambient Air Quality Standards for Particulate Matter

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Note: EPA no longer updates this information, but it may be useful as a reference or resource.

[Federal Register: July 18, 1997 (Rules and Regulations)]
[Page 38702-38752]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr18jy97-17]

[[Continued from page 38701]]

[[Page 38702]]

decisions make clear that the economic and technological feasibility of
attaining ambient standards are not to be considered in setting NAAQS,
although such factors may be considered in the development of State
plans to implement the standards. Accordingly, although, as described
below, a Regulatory Impact Analysis (RIA) has been prepared, neither
the RIA nor the associated contractor reports have been considered in
issuing this final rule.

A. Executive Order 12866

Under Executive Order 12866, 58 FR 51735 (October 4, 1993), the
Agency must determine whether a regulatory action is ``significant''
and, therefore, subject to Office of Management and Budget (OMB) review
and other requirements of the Executive Order. The order defines
``significant regulatory action'' as any regulatory action that is
likely to result in a rule that may:
(1) Have an annual effect on the economy of $100 million or more or
adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or tribal governments or
communities.
(2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another Agency.
(3) Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs or the rights and obligations of recipients
thereof.
(4) Raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
In view of its important policy implications, this action has been
judged to be a ``significant regulatory action'' within the meaning of
the Executive Order. As a result, under section 6 of the Executive
Order, EPA has prepared an RIA, entitled ``Regulatory Impact Analysis
for Particulate Matter and Ozone National Ambient Air Quality Standards
and Proposed Regional Haze Rule (July 1997).'' This RIA assesses the
costs, economic impacts, and benefits associated with potential State
implementation strategies for attaining the PM and O3 NAAQS
and the proposed Regional Haze Rule. Changes made in response to OMB
suggestions or recommendations will be documented in the public docket
and made available for public inspection at EPA's Air and Radiation
Docket Information Center (Docket No. A-95-58). The RIA will be
publicly available in hard copy by contacting the U.S. Environmental
Protection Agency Library at the address under ``Availability of
Related Information'' and in electronic form as discussed above in
``Electronic Availability.''

B. Regulatory Flexibility Analysis

The Regulatory Flexibility Act (RFA), 5 U.S.C. 601 et seq.,
provides that, whenever an agency is required to publish a general
notice of rulemaking for a proposal, the agency must prepare an initial
regulatory flexibility analysis for the proposal unless the head of the
agency certifies that the rule will not, if promulgated, have a
significant economic impact on a substantial number of small entities
(section 605(b)). The EPA certified the proposed NAAQS rule based on
its conclusion that the rule would not establish requirements
applicable to small entities and therefore would not have a significant
economic impact on small entities within the meaning of the RFA. See 61
FR 65638, 65668 (PM proposal) and 61 FR 65716, 65764 (ozone proposal),
both published December 13, 1996. Accordingly, the Agency did not
prepare an initial regulatory flexibility analysis for the proposal,
but it did conduct a more general analysis of the potential impact on
small entities of possible State strategies for implementing any new or
revised NAAQS.
At the heart of EPA's certification of the proposed NAAQS rule was
the Agency's interpretation of the word ``impact'' as used in the RFA.
Is the ``impact'' to be analyzed under the RFA a rule's impact on the
small entities that will be subject to the rule's requirements, or the
rule's impact on small entities in general, whether or not they will be
subject to the rule? In the case of NAAQS rules, the question arises
because of the congressionally designed mixture of Federal and State
responsibilities in setting and implementing the NAAQS.
As EPA explained in the proposal, NAAQS rules establish air quality
standards that States are primarily responsible for meeting. Under
section 110 and Part D of Title I of the Act, every State develops a
State Implementation Plan (SIP) containing the control measures that
will achieve a newly promulgated NAAQS. States have broad discretion in
the choice of control measures. As the U.S. Supreme Court noted in
Train v. NRDC, 421 U.S. 60 (1975), 95 S. Ct. 1470:

[P]rimary [NAAQS] deal with the quality of outdoor air and are
fixed on a nationwide basis at a level which the agency determines
will protect the public health. It is the attainment and maintenance
of these standards which section 110(a)(2)(A) requires that State
plans provide. In complying with this requirement, a State's plan
must include ``emission limitations'' which are regulations of the
composition of substances emitted into the ambient air from such
sources as power plants, service stations and the like. They are the
specific rules to which operators of pollution sources are subject
and which, if enforced, should result in ambient air which meets the
national standards.
The Agency is plainly charged by the Act with the responsibility
for setting the national ambient air standards. Just as plainly, it
is relegated to a secondary role in the process of determining and
enforcing the specific, source-by-source emission limitations which
are necessary if the national standards are to be met. Under
110(a)(2), the Agency is required to approve a State plan which
provides for the timely attainment and maintenance of the ambient
air standards, and which also satisfies that sections other general
requirements. The Act gives the agency no authority to question the
wisdom of a state's choices of emission limitations if they are part
of a plan which satisfies the standards of 110(a)(2) and the Agency
may devise and promulgate a plan of its own only if the State fails
to submit an implementation plan which satisfies those standards.
Section 110(c).

421 U.S. 60 at 78-79 (emphasis in original). In short, NAAQS rules
themselves do not establish any control requirements applicable to
small entities. State rules implementing the NAAQS may establish such
requirements and the extent to which they do depends primarily on each
State's strategy for meeting the NAAQS.⁹⁵
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95 It is worth noting that Federal rules that apply nationally
also play a role in reducing emissions governed by NAAQS. For
instance, EPA rules under Title II of the Act require reductions in
ozone-forming emissions from on and off-road vehicles and the fuels
that power them. When EPA issues such rules, it conducts the
analysis required under the RFA. For example, EPA performed
regulatory flexibility analyses for the reformulated gasoline rule
issued under section 211(k) of the Act. See 59 FR 7716, February 16,
1994.
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To determine the proper interpretation of impact under the RFA, EPA
considered the RFA's stated purpose, its requirements for regulatory
flexibility analyses, its legislative history, the amendments made by
the Small Business Regulatory Enforcement Fairness Act of 1996 (SBREFA)
(Pub. L. 104-121), and caselaw. The EPA concluded that all of these
traditional tools of statutory construction point in one direction--
that an agency is required to assess the impact of a rule on the small
entities that will be subject to the rule's requirements, because the
purpose of a regulatory flexibility analysis is to consider ways of
easing or even waiving a rule's requirements as they will apply to
small entities, consistent with the statute authorizing

[[Page 38703]]

the rule. That purpose cannot be served in the case of the rules like
the NAAQS that do not have requirements that apply to small entities.
More specifically, EPA noted that its interpretation of ``impact''
flows from the express purpose of the RFA itself. As the RFA's
``Findings and Purposes'' section (Pub. L. 96-354, section 2) makes
clear, Congress enacted the RFA in 1980 out of concern that agencies
were writing one-size-fits-all regulations that in fact did not fit the
size and resources of small entities. Congress noted that it is
generally easier for big businesses to comply with regulations, and
that small businesses are therefore at a competitive disadvantage in
complying with uniform rules. Congress also noted that small entities'
relative contribution to the problem a rule is supposed to solve may
not warrant applying the same requirements to large and small entities
alike. In the RFA itself, Congress therefore stated:

It is the purpose of this Act to establish as a principle of
regulatory issuance that agencies shall endeavor, consistent with
the objectives of the rule and of applicable statutes, to fit
regulatory and informational requirements to the scale of the
businesses, organizations, and governmental jurisdictions subject to
regulation.

(Pub. L. 96-354, section 2(b))
The EPA further noted that the RFA sections governing initial and
final regulatory flexibility analyses reflect this statement of
purpose. Sections 603 and 604 of the RFA require that initial and final
regulatory flexibility analyses identify the types and estimate the
numbers of small entities ``to which the proposed will apply''
(sections 603(b)(3) and 604(a)(3) of the RFA). Similarly, they require
a description of the ``projected reporting, recordkeeping, and other
compliance requirements of the proposal, including an estimate of the
classes of small entities which will be subject to the requirement''
(sections 603(b)(4) and 604(a)(4)). At the core of the analyses is the
requirement that agencies identify and consider ``significant
regulatory alternatives'' that would ``accomplish the stated objectives
of applicable statutes and which minimize any significant economic
impact of the proposal on small entities'' (sections 603(c) and
604(a)(5)). Among the types of alternatives agencies are to consider
are the establishment of different ``compliance or reporting
requirements or timetables'' for small entities and the exemption of
small entities ``from coverage of the rule, or any part'' of the rule
(section 603(c)(1) and (4) of the RFA). The RFA thus makes clear that
regulatory flexibility analyses are to focus on how to minimize rule
requirements on small entities.
As EPA further explained, since regulatory flexibility analyses are
not required for a rule that will not have a ``significant economic
impact on a substantial number of small entities'', it makes sense to
interpret ``impact'' in light of the requirements for such analyses.
Regulatory flexibility analyses, as described in this unit, are to
consider how a rule will apply to small entities and how its
requirements may be minimized with respect to small entities. In this
context, ``impact'' is appropriately interpreted to mean the impact of
a rule on the small entities subject to the rule's requirements.
The Agency cited two Federal court cases in support of its
interpretation. In Mid-Tex Elec. Co-op v. FERC, 773 F.2d 327, 342 (D.C.
Cir. 1985), petitioners claimed that the RFA required an agency to
analyze the effects of a rule on small entities that were not regulated
by the rule but might be indirectly impacted by it. Petitioners noted
that the Small Business Administration (SBA) also interpreted the RFA
to require analysis of a rule's impact on small entities not regulated
by the rule, and argued that the court should defer to the SBA's
position in light of its compliance monitoring role under the RFA.
After reviewing the RFA's ``Findings and Purposes'' section, its
legislative history, and its requirements for regulatory flexibility
analyses, the Mid-Tex court rejected petitioners' interpretation. As
the court explained:

The problem Congress stated it discerned was the high cost to
small entities of compliance with uniform regulations, and the
remedy Congress fashioned--careful consideration of those costs in
regulatory flexibility analyses--is accordingly limited to small
entities subject to the proposed regulation * * *. [W]e conclude
that an agency may properly certify that no regulatory flexibility
analysis is necessary when it determines that the rule will not have
a significant economic impact on a substantial number of small
entities that are subject to the requirements of the rule.

Id. at 342. Notably, Congress let this interpretation stand when it
recently amended the RFA in enacting SBREFA.
The EPA also cited a recent case affirming the Mid-Tex court's
interpretation. In United Distribution Companies v. FERC, 88 F.3d 1105,
1170 (D.C. Cir. 1996), the court noted that the Mid-Tex court:

* * * conducted an extensive analysis of RFA provisions
governing when a regulatory flexibility analysis is required and
concluded that no analysis is necessary when an agency determines
``that the rule will not have a significant economic impact on a
substantial number of small entities that are subject to the
requirements of the rule''.
Id., citing and quoting Mid-Tex (emphasis added by United Distribution
court). The Agency went on to explain that given the Federal/State
partnership for attaining healthy air, the proposed NAAQS, if adopted,
would not establish any requirements applicable to small entities.
Instead, any new or revised standard would establish levels of air
quality that States would be primarily responsible for achieving by
adopting plans containing specific control measures for that purpose.
The proposed NAAQS rule was thus not susceptible to regulatory
flexibility analysis as prescribed by the amended RFA. Since it would
establish no requirements applicable to small entities, it afforded no
opportunity for EPA to fashion for small entities less burdensome
compliance or reporting requirements or timetables, or exemptions from
all or part of the rule. For these reasons, EPA certified that the
proposal ``will not, if promulgated, have a significant economic impact
on a substantial number of small entities,'' within the meaning of the
RFA. Because EPA was not required to prepare an initial regulatory
flexibility analysis for the rule, it was also not required to convene
a Small Business Advocacy Review Panel for the rule under section
609(b) of the RFA, as added by SBREFA.
Notwithstanding its certification of the proposal, EPA recognized
that the proposed NAAQS, if adopted, would begin a process of State
implementation that could eventually lead to small entities having to
comply with new or different control measures, depending on the
implementation plans developed by the States. EPA also recognized that
the Act does not allow EPA to dictate or second-guess how States should
exercise their discretion in regulating to attain any new or revised
NAAQS. Under those circumstances, EPA concluded that the best way to
take account of small entity concerns regarding any new or revised
NAAQS was to work with small entity representatives and States to
provide information and guidance on how States could address small
entity concerns when they write their implementation plans.
In line with this approach, as part of RIA it prepared for the
proposed NAAQS, EPA analyzed how hypothetical State plans for
implementing the proposal might affect small entities. The analysis was
necessarily speculative and limited, since it depended on projections
about what States might do several years in the future and did not take
into account

[[Page 38704]]

any new strategies that might be developed and recommended by the FACA
subcommittee formed to help devise potential strategies for
implementing a new or revised NAAQS (see discussion of RIA and FACA
process in this document). Nevertheless, the analysis provided as much
information on potential small entity impacts as was reasonably
available at the time of the proposal.
The Agency also took steps to ensure that small entities' voices
were heard in the NAAQS rulemaking itself. With Jere Glover, Chief
Counsel for Advocacy of the SBA, EPA convened outreach meetings modeled
on the SBREFA panel process to solicit and convey small entities'
concerns with the proposed NAAQS. Two meetings were held as part of
that process, on January 7 and February 28, 1997, with a total
attendance of 41 representatives of small businesses, small
governments, and small nonprofit organizations. Both meetings were
attended by representatives of SBA and OMB, as well as of EPA. The key
concerns raised by small entities at those meetings related to the
scientific foundation of the proposed NAAQS and the potential cost of
implementing it, the same concerns raised by other industry commenters
on the proposal. The Agency produced a report on the meetings to ensure
that small entity concerns were part of the rulemaking record when EPA
made its final decision on the proposal.
In light of States' pivotal role in NAAQS implementation, EPA also
undertook a number of additional activities to assist and encourage the
States to be sensitive to small entity impacts as they implement any
new or revised NAAQS. With the SBA, EPA began an interagency panel
process to collect advice and recommendations from small entity
representatives on how States could lessen any impacts on small
entities. The EPA plans to issue materials in two phases to help States
develop their implementation plans. In view of States' discretion in
implementing the NAAQS, these materials will mostly take the form of
guidance, which is not subject to the RFA's requirement for initial
regulatory flexibility analysis. (Under section 603 of the RFA, that
requirement applies only to binding rules that are required to undergo
notice and comment rulemaking procedures.) But regardless of the form
such materials take, EPA is employing panel procedures to ensure that
small entities have an opportunity to raise any concerns prior to the
materials being issued in draft form.
To supplement the input the Agency receives from the ongoing FACA
process (described previously in this document), EPA also added more
small entity representatives to the Subcommittee on implementation of
any new or revised NAAQS. These representatives have formed a small
entity caucus to develop and bring to the Subcommittee a focused
approach to small entity issues. These new Subcommittee members are
also part of the group in the aforementioned panel process. By means of
these various processes, EPA hopes to promote the consideration of
small entity concerns and advice throughout the NAAQS implementation
process.
In response to the proposal, a number of commenters questioned
EPA's decision to certify that the proposed NAAQS will not have a
significant impact on a substantial number of small entities. Some
commenters disagreed with EPA's view that the proposed NAAQS would not
establish regulatory requirements applicable to small entities. These
commenters argued that a number of control requirements applicable to
small entities would automatically result from promulgation of the
proposed NAAQS, such as new reasonable further progress, SIP and
Federal Implementation Plan (FIP) requirements. Other commenters stated
that it is possible for EPA to assess the impacts of the NAAQS revision
on small entities and that, to a limited extent, EPA has already done
so. Further, a number of commenters argued that EPA has a legal
obligation under the RFA, as amended by SBREFA, to choose a NAAQS
alternative that minimizes the impact on small entities. Some
commenters questioned EPA's interpretations of the Mid-Tex and United
Distribution cases. In addition, other commenters stated that EPA's
position regarding the NAAQS and the RFA is inconsistent with its past
practice and the legislative history of the RFA. Finally, a few
commenters noted that the panel process EPA conducted for the proposed
NAAQS did not satisfy the requirements of SBREFA.
EPA disagrees that promulgation of the NAAQS will automatically
result in control requirements applicable to small entities that EPA
can and must analyze under the RFA. As noted previously in this unit, a
NAAQS rule only establishes a standard of air quality that other
provisions of the Act call on States (or in case of State inaction, the
Federal government) to achieve by adopting implementation plans
containing specific control measures for that purpose. Following
promulgation of a new or revised NAAQS, section 110 of the Act requires
States and EPA to engage in a designation process to determine what
areas within each State's borders are attaining or not attaining the
NAAQS. Under section 110 and Parts C and D of Title I of the Act,
States then conduct a planning process to develop and adopt their SIPS.
Depending on an area's designation for the particular NAAQS, these and
other Title I provisions of the Act require a State's SIP to contain
certain control programs in addition to the control measures that the
State decides are also needed to attain and maintain the NAAQS.
The fact that the Act requires SIPs to contain certain control
programs under certain circumstances does not mean that EPA either can
or must conduct a regulatory flexibility analysis of a rule
establishing a NAAQS. Just from the standpoint of feasibility, EPA
cannot know which areas will be subject to what mandatory SIP programs
until after the designation process is completed. Beyond that, any
mandatory SIP programs are still implemented by the States, and States
have considerable discretion in how they implement them. For instance,
the reasonable further progress requirement under section 172 of the
Act leaves States broad discretion to determine the rate of progress
and the control measures to achieve that progress.⁹⁶ As a
result, EPA cannot be certain where and how any mandatory programs will
be implemented with respect to small (or large) entities. Much less can
EPA know about how States will exercise their discretion to develop
additional controls needed to attain and maintain the NAAQS.
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96The SIP requirements of subpart 4 of Part D of Title I of the
Act apply to SIPs for areas designated as not attaining NAAQS for
PM10. Those requirements will not apply to SIPs to
implement the PM2.5 NAAQS. Further, to the extent SIPs
for areas in nonattainment with the applicable PM10 NAAQS
remain subject to subpart 4 requirements, there will be no
incremental change in the impact on sources regulated by the States'
SIPs pursuant to those requirements as a result of this
promulgation.
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Even if EPA could know exactly how any mandatory SIP programs would
apply to small entities, the purpose of the RFA is not served by
attempting a regulatory flexibility analysis of State implementation of
those programs. As explained previously in this unit, the RFA and the
caselaw interpreting it clearly establish that the purpose of the RFA
is to promote Federal agency efforts to tailor a rule's requirements to
the scale of the small entities that will be subject to it. That
purpose cannot be served in the case of a NAAQS rule since the rule
does not establish requirements applicable to small

[[Page 38705]]

entities. In promulgating a NAAQS, the only choice before EPA concerns
the level of the standard, not its implementation. While mandatory SIP
programs may ultimately follow from promulgation of the NAAQS, there is
nothing EPA can do in setting the NAAQS to tailor those programs as
they apply to small entities. Whether and how the programs will apply
in particular nonattainment areas is beyond the scope of the NAAQS
rulemaking and, indeed, beyond EPA's reach in any rulemaking to the
extent the applicability and terms of the programs are prescribed by
statute.⁹⁷ Moreover, any mandatory SIP programs are
supplemented by discretionary State controls that EPA has no power to
tailor under the RFA or the Act (see Train v. NRDC, quoted previously
in this unit).
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97 If and when the Agency issues any rules addressing State
implementation of any statutorily required actions, EPA would
analyze and address the impact of those rules on small entities as
appropriate under the RFA.
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The commenters' suggestions for minimizing the potential impact of
the NAAQS rule on small entities run afoul of both the RFA and the Act.
Some suggested that EPA set a less stringent standard (or no standard
at all in the case of PM2.5) to reduce the chance that small
entities would become subject to new or tighter SIP requirements.
Others suggested that EPA require States to exempt small entities from
new or tighter SIP requirements. However, as explained previously in
this document, the RFA neither requires nor authorizes EPA to set a
less stringent NAAQS than the applicable Clean Air Act provisions allow
in order to reduce potential small entity impacts. Indeed, the RFA
provides that any means of providing regulatory flexibility to small
entities be consistent with the statute authorizing the rule. Moreover,
even if EPA set a less stringent standard, States could still exercise
their discretion to obtain any needed emission reductions from small
entities. As the Supreme Court in Train v. NRDC made clear, EPA has no
authority to forbid States from obtaining reductions from any
particular category of stationary sources, including small entities.
See also, Virginia v. EPA, No. 108 F.3d 1397, 1408 (D.C. Cir. 1997),
quoting Union Electric v. EPA, 427 U.S. 246, 269 (1976) (``section 110
left to the states the power to determine which sources would be
burdened by regulations and to what extent'').
EPA's approval of SIPs for the new or revised NAAQS also will not
establish new requirements, but will instead simply approve
requirements that a State is already imposing. And again, EPA does not
have authority to disapprove a State's plan except to the extent that
the plan fails to demonstrate attainment and maintenance of the NAAQS
as required by Title I of the Clean Air Act. In cases where EPA
promulgates a FIP, EPA might establish control requirements applicable
to small entities, and in such a circumstance, EPA would conduct the
analyses required by the RFA.
Some commenters argued that under the RFA as amended by SBREFA, EPA
now has an obligation to choose the alternative that minimizes the
impact on small entities when setting the NAAQS. As indicated
previously in this unit, EPA disagrees with the commenters' argument
for the reasons stated in this document's discussion of the Agency's
authority to consider costs and other factors not related to public
health in setting and revising primary NAAQS. In a nutshell, both the
text and legislative history of the RFA make clear that the RFA does
not override the substantive provisions of the statute authorizing the
rule, but only requires agencies to identify and consider ways of
minimizing the economic impact on small entities subject to the rule in
a manner consistent with the authorizing statute.
Some commenters disagreed with EPA's interpretation of the Mid-Tex
and United Distribution cases. In particular, these commenters noted
that in those cases the relevant regulatory agency, Federal Energy
Regulatory Commission (FERC), wholly lacked jurisdiction to regulate
the small entities at issue. According to these commenters, EPA does
have the ability and jurisdiction to regulate small entities in the
case of the NAAQS, and therefore EPA's reliance on Mid-Tex and United
Distribution is misplaced.
The commenters' attempt to distinguish the FERC cases from the
NAAQS rulemaking wholly overlooks the courts' reasoning, which in fact
fully supports EPA's certification of the proposed NAAQS. As described
previously in this unit, the Mid-Tex court exhaustively reviewed the
relevant sections of the RFA and its legislative history. Its analysis
revealed that Congress passed the RFA out of concern with one-size-
fits-all regulations and fashioned a remedy limited to regulations that
apply to small entities. This principle is fully applicable to the
NAAQS, which creates no rule requirements that apply to small entities.
The fact that FERC had no regulatory authority over the small
entities indirectly affected by its rules played no essential role in
the court's rationale. FERC could (and apparently did in the Mid-Tex
rulemaking) estimate the potential indirect impact of its rules on
small entities. Presumably, FERC could have also mitigated any indirect
impact by changing some aspect of the rule (or else the small entities
would have had no incentive to sue the agency). The court nevertheless
found it unnecessary for FERC to do either, based on its reading of the
RFA as limited to analysis of a rule's impact on the small entities
subject to the rule's requirements. In reaching its decision, the court
noted that requiring agencies to ``consider every indirect effect that
any regulation might have on small businesses * * * is a very broad and
ambitious agenda, * * * that Congress is unlikely to have embarked on *
* * without airing the matter.'' Mid-Tex, 773 F.d. at 343.
The commenters also overstate EPA's regulatory authority over small
entities with respect to the regulation of criteria pollutants. Various
provisions of the Clean Air Act authorize EPA to regulate various types
of sources at the Federal level to accomplish specified goals. However,
EPA's authority to more generally regulate sources, including small
entities, in the manner of SIPs is limited to instances of State
default of SIP responsibilities. When that occurs, EPA may issue a FIP
containing specific control measures, and to the extent a proposed FIP
would establish control measures applicable to small entities, EPA
would analyze the small entity impact of those measures as required by
the RFA. In 1994, for example, EPA prepared an initial regulatory
flexibility analysis when it proposed a FIP for Los Angeles. See 59 FR
23264 (May 5, 1994).
As noted previously in this unit, Congress let the Mid-Tex
interpretation stand when it recently amended the RFA in enacting
SBREFA. If it had disagreed with the court's decision, it would have
revised the relevant statutory provisions or otherwise indicated its
disagreement when it enacted SBREFA. Instead, Congress actually
reinforced the Mid-Tex court's interpretation of the RFA in enacting
section 212(a) of SBREFA. That section requires that an agency issue a
``small entity compliance guide'' for ``each rule * * * for which an
agency is required to prepare a final regulatory flexibility analysis
under section 604'' of the RFA. The guide is ``to assist small entities
in complying with the rule'' by ``explain[ing] the actions a small
entity is required to take to comply'' with the rule (section 212(a) of
SBREFA). Obviously, it makes no sense to prepare a small entity
compliance guide for a rule that does not apply to small entities. Thus
SBREFA stands as further confirmation that Congress intended the

[[Page 38706]]

RFA to address only rules that establish requirements small entities
must meet. Since SBREFA's passage, the United Distribution court has
affirmed the Mid-Tex court's interpretation.
Some commenters noted that EPA's informal panel process did not
comply with the requirements of SBREFA. The EPA did not convene a
SBREFA panel because such a panel is not required for rules like the
NAAQS that do not apply to small entities. Under the RFA as amended by
SBREFA, since the Agency certified the proposal, it was not required to
convene a panel for it. Nevertheless, EPA conducted the voluntary panel
process described previously in this unit, as well as other voluntary
small business outreach efforts. The process could not comply with the
analytical requirements of the RFA for the reasons given in this unit.
However, it could and did ensure that EPA heard directly from small
entities about the NAAQS proposals.
A few commenters stated that EPA's view of the NAAQS and the RFA is
inconsistent with EPA's past positions regarding the RFA and NAAQS
revisions. Some commenters also cited the RIA for the proposed NAAQS
and noted that this analysis demonstrates EPA's ability to estimate the
impact of the NAAQS on small entities, thereby undercutting EPA's
argument that it is not able to perform a regulatory flexibility
analysis when setting the NAAQS.
Past Federal Register documents make clear that the nature of the
NAAQS makes a regulatory flexibility analysis inapplicable to NAAQS
rulemakings. For instance, in 1984, EPA stated that a ``NAAQS for
NO_X by itself has no direct impact on small entities.
However, it forces each State to design and implement control
strategies for areas not in attainment.'' See 49 FR 6866, 6876
(February 23, 1984); see also, 50 FR 37484, 37499 (September 13, 1985);
50 FR 25532, 25542 (June 19, 1985) (NAAQS for NO2 do not
impact small entities directly). EPA stated again in 1987 that the
NAAQS ``themselves do not contain emission limits or other pollution
controls. Rather, such controls are contained in state implementation
plans.'' See 52 FR 24634, 24654 (July 1, 1987).
EPA has typically performed an analysis to assess, to the extent
practicable, the potential impact of retaining or revising the NAAQS on
small entities, depending on possible State strategies for implementing
the NAAQS. These analyses have provided as much insight into the
potential small entity impacts of implementing revised NAAQS as could
be provided at the NAAQS rulemaking stage. In some instances, these
preliminary analyses were described as ``regulatory flexibility
analys[es]'' or as analyses ``pursuant to this [Regulatory Flexibility]
Act.'' See, e.g., 52 FR 24634, 24654 (July 1, 1987); 50 FR 37484, 37499
(September 13, 1985).
However, these analyses were based on hypothetical State control
strategies, and EPA made the point on various occasions that any
conclusions to be drawn from such analyses were speculative, given that
the NAAQS themselves do not impose requirements on small entities.
Although these past analyses reflected the Agency's best efforts to
evaluate potential impacts, they were not regulatory flexibility
analyses containing the necessary elements required by the RFA. These
analyses, for example, did not describe the reporting, recordkeeping,
and other compliance requirements of the proposed NAAQS rules that
would apply to small entities, since the NAAQS rules did not apply to
small entities. Nor did they determine how the proposed NAAQS rules
could be eased or waived for small entities. Such an analysis is not
possible in the case of the NAAQS. To the extent EPA labeled these
analyses regulatory flexibility analyses in the past, that label was
inappropriate. EPA's current practice is to describe such an analysis
more accurately as a general analysis of the potential cost impacts on
small entities. See, e.g., 61 FR 65638, 65669, 65747 (December 13,
1996) (current O3 and PM NAAQS proposals).⁹⁸
EPA's analytical approach to small entity impacts of the NAAQS has thus
remained consistent over time.
---------------------------------------------------------------------------

98 As commenters pointed out, the RIA for the proposed PM NAAQS
does state that ``[t]he screening analysis * * * provides enough
information for an initial regulatory flexibility analysis (RFA) if
such an analysis were to be done.'' That statement was mistaken and
was not made in the RIA for the proposed ozone NAAQS. While both
RIAs attempted to gauge the potential impact on small entities of
State implementation of the proposed NAAQS, neither could or did
identify any specific control or information requirements contained
in the NAAQS rule that would apply to small entities. Indeed, both
RIAs made clear that the impact being analyzed was that of potential
State measures to attain the NAAQS, and that such an analysis was
inherently speculative and uncertain. Thus, the RIAs actually
confirm EPA's statement in the preambles for the proposed NAAQS that
conducting a complete regulatory flexibility analysis is not
feasible for rules setting or revising a NAAQS.
---------------------------------------------------------------------------

One commenter noted that the legislative history of the RFA
suggests that the RFA was intended to apply to the NAAQS. As noted
previously in this unit, EPA's reading of both the RFA and SBREFA,
based on the language of the statute as amended and its legislative
histories and applicable caselaw, is that the RFA requirements at issue
do not apply to the NAAQS. The legislative history cited by the
commenter does not change this conclusion.
In fact, the statement by Senator Culver on which the commenter
relies does not indicate that the NAAQS should be subject to regulatory
flexibility analyses. Rather, Senator Culver uses the NAAQS as an
example of the type of standard that agencies would not change as a
result of the RFA. According to Senator Culver, section 606 of the RFA
``succinctly states that this bill does not alter the substantive
standard contained in underlying statutes which defines the agency's
mandate.'' 126 Cong. Rec. S 21455 (August 6, 1980) daily ed. After
citing section 109 of the Act, Senator Culver goes on to describe EPA's
bubble policy (which addresses the limits on emissions from a
particular facility) as the type of flexible regulation that agencies
should consider, once EPA has set a NAAQS. ``The important point for
purposes of this discussion is that the `bubble concept,' a type of
flexible regulation, in no manner altered the basic statutory
substantive standard of the EPA * * *. No regulatory flexibility
analysis alters the substantive standard otherwise applicable by law to
agency action.'' Id. Thus, contrary to the suggestion of the commenter,
Senator Culver's statement actually confirms that the time to consider
regulatory flexibility is when regulations applicable to sources are
being established, not when a NAAQS itself is being set.
Under section 604 of the RFA, whenever an agency promulgates a
final rule under section 553 of the Administrative Procedure Act, after
being required by that section or any other law to publish a general
notice of proposed rulemaking (NPRM), the agency is required to prepare
a final regulatory flexibility analysis. RFA section 605(b) provides,
however, that section 603 (re initial regulatory flexibility analyses)
and section 604 do not apply if the agency certifies that the rule will
not have a significant economic impact on a substantial number of small
entities and publishes such certification at the time of publication of
the NPRM or at the time of the final rule.
As noted above, EPA certified this final rule at the time of the
NPRM. After considering the public comments on the certification, EPA
continues to believe that this final rule will not have a significant
economic impact on a substantial number of small entities for the
reasons explained above and that it

[[Page 38707]]

therefore appropriately certified the rule. Further, as required by the
Clean Air Act, EPA is promulgating this final rule under section 307(d)
of the Clean Air Act. For all the foregoing reasons, EPA has not
prepared a final regulatory flexibility analysis for the rule. The
Agency has nonetheless analyzed in the final RIA for the rule the
potential impact on small entities of hypothetical State plans for
implementing the NAAQS. The Agency also plans to issue guidance to the
States on reducing the potential impact on small entities of
implementing the NAAQS.

C. Impact on Reporting Requirements

There are no reporting requirements directly associated with the
finalization of ambient air quality standards under section 109 of the
Act (42 U.S.C. 7400). There are, however, reporting requirements
associated with related sections of the Act, particularly sections 107,
110, 160, and 317 (42 U.S.C. 7407, 7410, 7460, and 7617).
In EPA's final revisions to the air quality surveillance
requirements (40 CFR part 58) for PM, the associated RIA addresses the
Paperwork Reduction Act requirements through an Information Collection
Request.

D. Unfunded Mandates Reform Act

Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Pub.
L. 104-4, establishes requirements for Federal agencies to assess the
effects of certain regulatory actions on State, local, and tribal
governments and the private sector. Under section 202 of UMRA, EPA
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures by State, local, and tribal governments, in
the aggregate, or by the private sector, of $100 million or more in any
1 year. This requirement does not apply if EPA is prohibited by law
from considering section 202 of UMRA estimates and analyses in adopting
the rule in question. Before promulgating a final rule for which a
written statement is needed, section 205 of UMRA generally requires EPA
to identify and consider a reasonable number of regulatory alternatives
and adopt the least costly, most cost-effective, or least burdensome
alternative that achieves the objectives of the rule. These
requirements do not apply when they are inconsistent with applicable
law. Moreover, section 205 of UMRA allows EPA to adopt an alternative
other than the least costly, most cost-effective, or least burdensome
alternative if the Administrator publishes with the final rule an
explanation of why that alternative was not adopted. Before EPA
establishes any regulatory requirements that may significantly or
uniquely affect small governments, including tribal governments, it
must have developed under section 203 of UMRA a small government agency
plan. The plan must provide for notifying potentially affected small
governments, enabling officials of affected small governments to have
meaningful and timely input in the development of EPA regulatory
proposals with significant Federal intergovernmental mandates, and
informing, educating, and advising small governments on compliance with
the regulatory requirements. Section 204 of UMRA requires each agency
to develop ``an effective process to permit elected officers of state,
local and tribal governments * * * to provide meaningful and timely
input'' in the development of regulatory proposals containing a
significant Federal intergovernmental mandate.⁹⁹
---------------------------------------------------------------------------

99 As noted in unit VIII.B., a NAAQS rule only establishes a
standard of air quality that other provisions of the Act call on
States (or in the case of State inaction, the Federal government) to
achieve by adopting implementation plans containing specific control
measures for the purpose. Thus, it is questionable whether the NAAQS
itself imposes an enforceable duty and thus whether it is a
significant Federal mandate within the meaning of UMRA. EPA need not
and does not reach this issue in this document. For the reasons
given in this unit, even if the NAAQS were determined to be a
significant Federal mandate, EPA does not have any obligations under
sections 202 and 205 of UMRA, and EPA has met any obligations it
would have under section 204 of UMRA.
---------------------------------------------------------------------------

The EPA has determined that the provisions of sections 202 and 205
of UMRA do not apply to this decision.``Unless otherwise prohibited by
law,'' EPA is to prepare a written statement under section 202 of UMRA
that is to contain assessments and estimates of the costs and benefits
of a rule containing a Federal mandate. Congress clarified that
``unless otherwise prohibited by law'' referred to whether an agency
was prohibited from considering the information in the rulemaking
process, not to whether an agency was prohibited from collecting the
information. The Conference Report on UMRA states, ``This section [202]
does not require the preparation of any estimate or analysis if the
agency is prohibited by law from considering the estimate or analysis
in adopting the rule.'' 141 Cong. Rec. H3063 (daily ed. March 13,
1995). Because the Clean Air Act prohibits EPA, when setting the NAAQS,
from considering the types of estimates and assessments described in
section 202 of UMRA, UMRA does not require EPA to prepare a written
statement under section 202.¹00 The requirements in section
205 of UMRA do not apply because those requirements only apply to rules
``for which a written statement is required under section 202 * * *.''
---------------------------------------------------------------------------

100In addition to the estimates and assessments described in
section 202 of UMRA, written statements are also to include an
identification of the Federal law under which the rule is
promulgated (section 202(a)(1) of UMRA) and a description of
outreach efforts under section 204 of UMRA (section 202(a)(5) of
UMRA). Although these requirements do not apply here because a
written statement is not required under section 202 of UMRA, this
preamble identifies the Federal law under which this rule is being
promulgated and a written statement describing EPA's outreach
efforts with State, local, and tribal governments will be placed in
the docket.
---------------------------------------------------------------------------

The EPA has determined that the provisions of section 203 of UMRA
do not apply to this decision. Section 203 of UMRA only requires the
development of a small government agency plan for requirements with
which small governments might have to comply. Since setting the NAAQS
does not establish requirements with which small governments might have
to comply, section 203 of UMRA does not apply. The EPA acknowledges,
however, that any corresponding revisions to associated SIP
requirements and air quality surveillance requirements, 40 CFR parts 51
and 58, respectively, might result in such effects.Accordingly, EPA did
address unfunded mandates when it proposed revisions to 40 CFR part 58,
and will do so, as appropriate, when it proposes any revision to 40 CFR
part 51.
With regard to the outreach described in section 204 of UMRA, EPA
did follow a process for providing elected officials with an
opportunity for meaningful and timely input into the proposed NAAQS
revisions, although EPA did not describe this process in the proposal.
The EPA conducted a series of pre-proposal outreach meetings with State
and local officials and their representatives that permitted these
officials to provide meaningful and timely input on issues related to
the NAAQS and the monitoring issues associated with them. Beginning in
January, 1996, EPA briefed State and local air pollution control
officials at national meetings with State and Territorial Air Pollution
Program Administrators (STAPPA) / Association of Local Air Pollution
Control Officials (ALAPCO) in Washington, DC, North Carolina, Chicago,
and Nevada. The EPA also held briefings for the Washington, DC
representatives of several State and local organizations, including
National Conference of State Legislators, U.S. Conference of Mayors,

[[Page 38708]]

National Governors Association, National League of Cities, and STAPPA/
ALAPCO. EPA also held separate briefings and discussions with State and
local officials at meetings set up by the National Governors
Association, the U.S. Conference of Mayors and the Council of State
Governments. The EPA also conducted in-depth briefings at each EPA
regional office and regional staff also had several meetings and
discussions with their State counterparts about the standards. The
efforts described in this paragraph of this preamble, which provided
elected officials with opportunity for meaningful and timely input into
the proposed NAAQS revisions, met any requirements imposed by section
204 of UMRA. The docket will contain a written statement describing
these outreach efforts, including a summary of the comments and
concerns presented by State, local, and tribal governments and a
summary of EPA's evaluation of those comments and concerns.
Several commenters disagreed with EPA that sections 202, 203, and
205 of UMRA do not apply to this decision. These commenters argued that
EPA is not prohibited from considering costs in setting NAAQS under the
Clean Air Act and applicable judicial decisions. Some commenters also
expressed the view that there is no conflict between UMRA and the Clean
Air Act with regard to the NAAQS. These commenters argued that UMRA and
the NAAQS can be harmonized by reading UMRA as an information gathering
statute and that EPA should therefore perform the analyses required by
UMRA, regardless of whether costs may be considered. Finally, at least
one commenter argued that in past NAAQS reviews, EPA did not dispute
its UMRA obligations.
As discussed more fully in Unit IV. of this preamble, EPA is
prohibited from considering cost in setting the NAAQS. Given that fact
(as noted in Unit IV. of this preamble), sections 202 and 205 of UMRA
do not apply.¹01 As the Conference Report clarifies, UMRA
itself states that the section 202 estimates and analyses are not
required in cases such as the NAAQS, where an agency is prohibited by
law from considering section 202 estimates and analyses. Reading UMRA
in the manner suggested by the commenters would effectively read this
provision out of UMRA; UMRA contains an exception for rules like the
NAAQS, it must be given effect.
---------------------------------------------------------------------------

101 One commenter argued that in reviewing the SO2
NAAQS, EPA determined that it need not revise the S02
NAAQS, but could instead pursue an alternative regulatory program
under other authority. This commenter argued that EPA has similar
flexibility in reviewing the PM and Ozone NAAQS, and thus UMRA
requires EPA to identify the least burdensome alternative (such as
retaining the current NAAQS) as part of that process. As discussed
more fully in Unit IV. of this preamble, EPA does not agree that it
has flexibility to choose such an alternative; nor does EPA agree
with the commenter's characterization of the action it took in
deciding not to revise the SO2 NAAQS. In fact, in
deciding not to revise the SO2 NAAQS, EPA determined, for
reasons independent of section 303 of the Clean Air Act that a NAAQS
revision was not warranted. See 61 FR 25566, 25575 (May 22, 1996).
---------------------------------------------------------------------------

With regard to EPA's position regarding UMRA in previous NAAQS
review exercises, EPA simply made plain in those situations that
because it did not plan on revising the NAAQS, it determined, without
further review, that sections 202, 203, and 205 of UMRA did not apply.
EPA thus stated that:

Because the Administrator has decided not to revise the existing
primary NAAQS for SO2, this action will not impose any
new expenditures on governments or on the private sector, or
establish any new regulatory requirements affecting small
governments. Accordingly, EPA has determined that the provisions of
sections 202, 203 and 205 do not apply to this final decision.

61 FR 25566, 25577, May 22, 1996; see also 61 FR 52852, 52856, October
8, 1996 (Same statement for NO2 NAAQS). As this statement
makes clear, EPA only determined that sections 202, 203, and 205 of
UMRA did not apply to the NAAQS when EPA fails to revise the standard.
Having made that determination, EPA had no reason to catalog additional
bases for finding UMRA inapplicable. Nothing in that statement was
intended to preclude EPA, or precludes EPA, from concluding for other
reasons (such as those discussed in this unit) that UMRA also does not
apply when EPA in fact revises an applicable NAAQS.

E. Environmental Justice

Executive Order 12848 (58 FR 7629, February 11, 1994) requires that
each Federal agency make achieving environmental justice part of its
mission by identifying and addressing, as appropriate,
disproportionately high and adverse human health or environmental
effects of its programs, policies, and activities on minorities and
low-income populations. These requirements have been addressed to the
extent practicable in the RIA cited in this unit.

F. Submission to Congress and the Comptroller General

Under 5 U.S.C. 801(a)(1)(A), as added by the Small Business
Regulatory Enforcement Fairness Act of 1996 (SBREFA), EPA submitted a
report containing this rule and other required information to the U.S.
Senate, the U.S. House of Representatives, and the Comptroller General
of the United States prior to publication of the rule in this issue of
the Federal Register. This rule is a ``major rule'' for purposes of
SBREFA.

IX. Response to Petition for Administrator Browner's Rescusal

On March 13, 1997, the Washington Legal Foundation (WLF), filed a
petition with EPA asking that I, Carol Browner, disqualify myself in
rulemaking regarding the NAAQS for PM and ozone. The petition claims
that my public statements indicate a ``clear and convincing showing''
that I had ``already decided to revise the NAAQS for PM and ozone'' and
that I therefore ``could not give meaningful consideration`` to
comments adverse to the proposed rule. On May 12, 1997, EPA's General
Counsel, Jonathan Z. Cannon, sent a letter to WLF regarding the
petition. This letter and the WLF petition were then placed in the
dockets for the proposed ozone and PM standards pending ``consideration
and final response in connection with the Agency's final actions.''
Contrary to WLF's assertions, I have maintained an open mind
throughout these proceedings, and have based today's decisions on the
rulemaking record--including consideration of comments opposed to the
proposal. The law does not require the Administrator of EPA to
disqualify herself merely for expressing views on a proposed
regulation; in fact, it is part of my responsibility to engage in the
public debate on the proposals. Moreover, the assertions in WLF's
petition do not accurately represent my views. The petition takes
quotes out of context and repeatedly misinterprets my statements. For
example, WLF quotes a statement that I made at the Children's
Environmental Health Network Research Conference as an indication that
I had ``prejudged the issue.'' However, my statement that ``I will not
be swayed'' did not refer to adopting the NAAQS as proposed. Instead,
as is clear from reviewing the entire speech, I was addressing my
broader concern about children's health and the range of EPA standards
affecting children's health. I also appeared at several congressional
hearings and testified before members of Congress, some of whom were
strongly opposed to the proposals. At those hearings, I explained the
basis for the proposals and put forward the reasons why I concluded the
proposals were appropriate, given the information before me at the
time. At the same time, I made clear that I took very seriously

[[Page 38709]]

my obligation to keep an open mind, and to consider fully and fairly
all significant comments that the Agency received. For these reasons
and others, as set forth in Mr. Cannon's May 12, 1997 response to WLF,
which I adopt in full, I have decided not to recuse myself from any
aspect of considering revisions to the NAAQS for ozone and PM.
Accordingly, I am hereby denying WLF's petition.

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(37) Katsouyanni, K.; Touloumi, G.; Spix, C.; Schwartz, J.;
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List of Subjects in 40 CFR Part 50

Environmental protection, Air pollution control, Carbon monoxide,
Lead, Nitrogen dioxide, Ozone, Particulate matter, Sulfur oxides.

Dated: July 16, 1997.

Carol M. Browner,
Administrator.

Therefore, 40 CFR Chapter I is amended as follows:

PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY
STANDARDS

1. The authority citation for part 50 continues to read as follows:

Authority: Secs. 109 and 301(a), Clean Air Act, as amended (42
U.S.C. 7409, 7601(a)).

2. Section 50.3 is revised to read as follows:

Sec. 50.3 Reference conditions.

All measurements of air quality that are expressed as mass per unit
volume (e.g., micrograms per cubic meter) other than for the
particulate matter (PM10 and PM2.5) standards
contained in Sec. 50.7 shall be corrected to a reference temperature of
25 deg.C and a reference pressure of 760 millimeters of mercury
(1,013.2 millibars). Measurements of PM10 and
PM2.5 for purposes of comparison to the standards contained
in Sec. 50.7 shall be reported based on actual ambient air volume
measured at the actual ambient temperature and pressure at the
monitoring site during the measurement period.
3. Section 50.6 is amended by revising the section heading and
adding paragraph (d) to read as follows:

Sec. 50.6 National primary and secondary ambient air quality
standards for PM10.

* * * * *
(d) The PM10 standards set forth in this section will no
longer apply to an area not attaining these standards as of September
16, 1997, once EPA takes final action to promulgate a rule pursuant to
section 172(e) of the Clean Air Act, as amended (42 U.S.C. 7472(e))
applicable to the area. The PM10 standards set forth in this
section will no longer apply to an area attaining these standards as of
September 16, 1997, once EPA approves a State Implementation Plan (SIP)
applicable to the area containing all PM10 control measures
adopted and implemented by the state prior to September 16, 1997, and a
section 110 SIP implementing the PM standards published on July 18,
1997. SIP approvals are codified in 40 CFR part 52.
4. Section 50.7 is added to read as follows:

Sec. 50.7 National primary and secondary ambient air quality
standards for particulate matter.

(a) The national primary and secondary ambient air quality
standards for particulate matter are:
(1) 15.0 micrograms per cubic meter (g/m³)
annual arithmetic mean concentration, and 65 g/m³
24-hour average concentration measured in the ambient air as
PM2.5 (particles with an aerodynamic diameter less than or
equal to a nominal 2.5 micrometers) by either:
(i) A reference method based on Appendix L of this part and
designated in accordance with part 53 of this chapter; or
(ii) An equivalent method designated in accordance with part 53 of
this chapter.
(2) 50 micrograms per cubic meter (g/m³) annual
arithmetic mean

[[Page 38712]]

concentration, and 150 g/m³ 24-hour average
concentration measured in the ambient air as PM10 (particles
with an aerodynamic diameter less than or equal to a nominal 10
micrometers) by either:
(i) A reference method based on Appendix M of this part and
designated in accordance with part 53 of this chapter; or
(ii) An equivalent method designated in accordance with part 53 of
this chapter.
(b) The annual primary and secondary PM2.5 standards are
met when the annual arithmetic mean concentration, as determined in
accordance with Appendix N of this part, is less than or equal to 15.0
micrograms per cubic meter.
(c) The 24-hour primary and secondary PM2.5 standards
are met when the 98^th percentile 24-hour concentration, as
determined in accordance with Appendix N of this part, is less than or
equal to 65 micrograms per cubic meter.
(d) The annual primary and secondary PM10 standards are
met when the annual arithmetic mean concentration, as determined in
accordance with Appendix N of this part, is less than or equal to 50
micrograms per cubic meter.
(e) The 24-hour primary and secondary PM10 standards are
met when the 99^th percentile 24-hour concentration, as
determined in accordance with Appendix N of this part, is less than or
equal to 150 micrograms per cubic meter.
5. Appendix K is revised (for conformity with the format of the
other appendices in this part) to read as follows:

Appendix K to Part 50--Interpretation of the National Ambient Air
Quality Standards for Particulate Matter

1.0 General.
(a) This appendix explains the computations necessary for
analyzing particulate matter data to determine attainment of the 24-
hour and annual standards specified in 40 CFR 50.6. For the primary
and secondary standards, particulate matter is measured in the
ambient air as PM10 (particles with an aerodynamic
diameter less than or equal to a nominal 10 micrometers) by a
reference method based on appendix J of this part and designated in
accordance with part 53 of this chapter, or by an equivalent method
designated in accordance with part 53 of this chapter. The required
frequency of measurements is specified in part 58 of this chapter.
(b) The terms used in this appendix are defined as follows:
Average refers to an arithmetic mean. All particulate matter
standards are expressed in terms of expected annual values: Expected
number of exceedances per year for the 24-hour standards and
expected annual arithmetic mean for the annual standards.
Daily value for PM10 refers to the 24-hour average
concentration of PM10 calculated or measured from
midnight to midnight (local time).
Exceedance means a daily value that is above the level of the
24-hour standard after rounding to the nearest 10 g/m\3\
(i.e., values ending in 5 or greater are to be rounded up).
Expected annual value is the number approached when the annual
values from an increasing number of years are averaged, in the
absence of long-term trends in emissions or meteorological
conditions.
Year refers to a calendar year.
(c) Although the discussion in this appendix focuses on
monitored data, the same principles apply to modeling data, subject
to EPA modeling guidelines.
2.0 Attainment Determinations.
2.1 24-Hour Primary and Secondary Standards.
(a) Under 40 CFR 50.6(a) the 24-hour primary and secondary
standards are attained when the expected number of exceedances per
year at each monitoring site is less than or equal to one. In the
simplest case, the number of expected exceedances at a site is
determined by recording the number of exceedances in each calendar
year and then averaging them over the past 3 calendar years.
Situations in which 3 years of data are not available and possible
adjustments for unusual events or trends are discussed in sections
2.3 and 2.4 of this appendix. Further, when data for a year are
incomplete, it is necessary to compute an estimated number of
exceedances for that year by adjusting the observed number of
exceedances. This procedure, performed by calendar quarter, is
described in section 3.0 of this appendix. The expected number of
exceedances is then estimated by averaging the individual annual
estimates for the past 3 years.
(b) The comparison with the allowable expected exceedance rate
of one per year is made in terms of a number rounded to the nearest
tenth (fractional values equal to or greater than 0.05 are to be
rounded up; e.g., an exceedance rate of 1.05 would be rounded to
1.1, which is the lowest rate for nonattainment).
2.2 Annual Primary and Secondary Standards. Under 40 CFR
50.6(b), the annual primary and secondary standards are attained
when the expected annual arithmetic mean
PM10 concentration is less than or equal to the level of
the standard. In the simplest case, the expected annual arithmetic
mean is determined by averaging the annual arithmetic mean
PM10 concentrations for the past 3 calendar years.
Because of the potential for incomplete data and the possible
seasonality in PM10 concentrations, the annual mean shall
be calculated by averaging the four quarterly means of
PM10 concentrations within the calendar year. The
equations for calculating the annual arithmetic mean are given in
section 4.0 of this appendix. Situations in which 3 years of data
are not available and possible adjustments for unusual events or
trends are discussed in sections 2.3 and 2.4 of this appendix. The
expected annual arithmetic mean is rounded to the nearest 1
g/m\3\ before comparison with the annual standards
(fractional values equal to or greater than 0.5 are to be rounded
up).
2.3 Data Requirements.
(a) 40 CFR 58.13 specifies the required minimum frequency of
sampling for PM10. For the purposes of making comparisons
with the particulate matter standards, all data produced by National
Air Monitoring Stations (NAMS), State and Local Air Monitoring
Stations (SLAMS) and other sites submitted to EPA in accordance with
the Part 58 requirements must be used, and a minimum of 75 percent
of the scheduled PM10 samples per quarter are required.
(b) To demonstrate attainment of either the annual or 24-hour
standards at a monitoring site, the monitor must provide sufficient
data to perform the required calculations of sections 3.0 and 4.0 of
this appendix. The amount of data required varies with the sampling
frequency, data capture rate and the number of years of record. In
all cases, 3 years of representative monitoring data that meet the
75 percent criterion of the previous paragraph should be utilized,
if available, and would suffice. More than 3 years may be
considered, if all additional representative years of data meeting
the 75 percent criterion are utilized. Data not meeting these
criteria may also suffice to show attainment; however, such
exceptions will have to be approved by the appropriate Regional
Administrator in accordance with EPA guidance.
(c) There are less stringent data requirements for showing that
a monitor has failed an attainment test and thus has recorded a
violation of the particulate matter standards. Although it is
generally necessary to meet the minimum 75 percent data capture
requirement per quarter to use the computational equations described
in sections 3.0 and 4.0 of this appendix, this criterion does not
apply when less data is sufficient to unambiguously establish
nonattainment. The following examples illustrate how nonattainment
can be demonstrated when a site fails to meet the completeness
criteria. Nonattainment of the 24-hour primary standards can be
established by the observed annual number of exceedances (e.g., four
observed exceedances in a single year), or by the estimated number
of exceedances derived from the observed number of exceedances and
the required number of scheduled samples (e.g., two observed
exceedances with every other day sampling). Nonattainment of the
annual standards can be demonstrated on the basis of quarterly mean
concentrations developed from observed data combined with one-half
the minimum detectable concentration substituted for missing values.
In both cases, expected annual values must exceed the levels allowed
by the standards.
2.4 Adjustment for Exceptional Events and Trends.
(a) An exceptional event is an uncontrollable event caused by
natural sources of particulate matter or an event that is not
expected to recur at a given location. Inclusion of such a value in
the computation of exceedances or averages could result in
inappropriate estimates of their respective expected annual values.
To reduce the effect of unusual events, more than 3 years of

[[Page 38713]]

representative data may be used. Alternatively, other techniques,
such as the use of statistical models or the use of historical data
could be considered so that the event may be discounted or weighted
according to the likelihood that it will recur. The use of such
techniques is subject to the approval of the appropriate Regional
Administrator in accordance with EPA guidance.
(b) In cases where long-term trends in emissions and air quality
are evident, mathematical techniques should be applied to account
for the trends to ensure that the expected annual values are not
inappropriately biased by unrepresentative data. In the simplest
case, if 3 years of data are available under stable emission
conditions, this data should be used. In the event of a trend or
shift in emission patterns, either the most recent representative
year(s) could be used or statistical techniques or models could be
used in conjunction with previous years of data to adjust for
trends. The use of less than 3 years of data, and any adjustments
are subject to the approval of the appropriate Regional
Administrator in accordance with EPA guidance.
3.0 Computational Equations for the 24-hour Standards.
3.1 Estimating Exceedances for a Year.
(a) If PM10 sampling is scheduled less frequently
than every day, or if some scheduled samples are missed, a
PM10 value will not be available for each day of the
year. To account for the possible effect of incomplete data, an
adjustment must be made to the data collected at each monitoring
location to estimate the number of exceedances in a calendar year.
In this adjustment, the assumption is made that the fraction of
missing values that would have exceeded the standard level is
identical to the fraction of measured values above this level. This
computation is to be made for all sites that are scheduled to
monitor throughout the entire year and meet the minimum data
requirements of section 2.3 of this appendix. Because of possible
seasonal imbalance, this adjustment shall be applied on a quarterly
basis. The estimate of the expected number of exceedances for the
quarter is equal to the observed number of exceedances plus an
increment associated with the missing data. The following equation
must be used for these computations:

Equation 1
[GRAPHIC] [TIFF OMITTED] TR18JY97.180

where:

eq=the estimated number of exceedances for calendar
quarter q;

vq=the observed number of exceedances for calendar
quarter q;

Nq=the number of days in calendar quarter q;

nq=the number of days in calendar quarter q with
PM10 data; and

q=the index for calendar quarter, q=1, 2, 3 or 4.

(b) The estimated number of exceedances for a calendar quarter
must be rounded to the nearest hundredth (fractional values equal to
or greater than 0.005 must be rounded up).
(c) The estimated number of exceedances for the year, e, is the
sum of the estimates for each calendar quarter.

Equation 2
[GRAPHIC] [TIFF OMITTED] TR18JY97.181

(d) The estimated number of exceedances for a single year must
be rounded to one decimal place (fractional values equal to or
greater than 0.05 are to be rounded up). The expected number of
exceedances is then estimated by averaging the individual annual
estimates for the most recent 3 or more representative years of
data. The expected number of exceedances must be rounded to one
decimal place (fractional values equal to or greater than 0.05 are
to be rounded up).
(e) The adjustment for incomplete data will not be necessary for
monitoring or modeling data which constitutes a complete record,
i.e., 365 days per year.
(f) To reduce the potential for overestimating the number of
expected exceedances, the correction for missing data will not be
required for a calendar quarter in which the first observed
exceedance has occurred if:
(1) There was only one exceedance in the calendar quarter;
(2) Everyday sampling is subsequently initiated and maintained
for 4 calendar quarters in accordance with 40 CFR 58.13; and
(3) Data capture of 75 percent is achieved during the required
period of everyday sampling. In addition, if the first exceedance is
observed in a calendar quarter in which the monitor is already
sampling every day, no adjustment for missing data will be made to
the first exceedance if a 75 percent data capture rate was achieved
in the quarter in which it was observed.

Example 1

a. During a particular calendar quarter, 39 out of a possible 92
samples were recorded, with one observed exceedance of the 24-hour
standard. Using Equation 1, the estimated number of exceedances for
the quarter is:

eq=1 x 92/39=2.359 or 2.36.

b. If the estimated exceedances for the other 3 calendar
quarters in the year were 2.30, 0.0 and 0.0, then, using Equation 2,
the estimated number of exceedances for the year is
2.36+2.30+0.0+0.0 which equals 4.66 or 4.7. If no exceedances were
observed for the 2 previous years, then the expected number of
exceedances is estimated by: (1/3) x (4.7+0+0)=1.57 or 1.6. Since
1.6 exceeds the allowable number of expected exceedances, this
monitoring site would fail the attainment test.

Example 2

In this example, everyday sampling was initiated following the
first observed exceedance as required by 40 CFR 58.13. Accordingly,
the first observed exceedance would not be adjusted for incomplete
sampling. During the next three quarters, 1.2 exceedances were
estimated. In this case, the estimated exceedances for the year
would be 1.0+1.2+0.0+0.0 which equals 2.2. If, as before, no
exceedances were observed for the two previous years, then the
estimated exceedances for the 3-year period would then be (1/
3) x (2.2+0.0+0.0)=0.7, and the monitoring site would not fail the
attainment test.
3.2 Adjustments for Non-Scheduled Sampling Days.
(a) If a systematic sampling schedule is used and sampling is
performed on days in addition to the days specified by the
systematic sampling schedule, e.g., during episodes of high
pollution, then an adjustment must be made in the eqution for the
estimation of exceedances. Such an adjustment is needed to eliminate
the bias in the estimate of the quarterly and annual number of
exceedances that would occur if the chance of an exceedance is
different for scheduled than for non-scheduled days, as would be the
case with episode sampling.
(b) The required adjustment treats the systematic sampling
schedule as a stratified sampling plan. If the period from one
scheduled sample until the day preceding the next scheduled sample
is defined as a sampling stratum, then there is one stratum for each
scheduled sampling day. An average number of observed exceedances is
computed for each of these sampling strata. With nonscheduled
sampling days, the estimated number of exceedances is defined as:

Equation 3
[GRAPHIC] [TIFF OMITTED] TR18JY97.182

where:

eq=the estimated number of exceedances for the quarter;

Nq=the number of days in the quarter;

mq=the number of strata with samples during the quarter;

vj=the number of observed exceedances in stratum j; and

kj=the number of actual samples in stratum j.

Example 3

A monitoring site samples according to a systematic sampling
schedule of one sample every 6 days, for a total of 15 scheduled
samples in a quarter out of a total of 92 possible samples. During
one 6-day period, potential episode levels of PM10 were
suspected, so 5 additional samples were taken. One of the regular
scheduled samples was missed, so a total of 19 samples in 14
sampling strata were measured. The one 6-day sampling stratum with 6
samples recorded 2 exceedances. The remainder of the quarter with
one sample per stratum recorded zero exceedances. Using Equation 3,
the estimated number of exceedances for the quarter is:

eq=(92/14) x (2/6+0+. . .+0)=2.19.

[[Page 38714]]

4.0 Computational Equations for Annual Standards.
4.1 Calculation of the Annual Arithmetic Mean. (a) An annual
arithmetic mean value for PM10 is determined by averaging
the quarterly means for the 4 calendar quarters of the year. The
following equation is to be used for calculation of the mean for a
calendar quarter:

Equation 4
[GRAPHIC] [TIFF OMITTED] TR18JY97.183

where:
xq= the quarterly mean concentration for quarter q, q=1,
2, 3, or 4,

nq= the number of samples in the quarter, and

xi= the ith concentration value recorded in the quarter.

(b) The quarterly mean, expressed in g/m\3\, must be
rounded to the nearest tenth (fractional values of 0.05 should be
rounded up).
(c) The annual mean is calculated by using the following
equation:

Equation 5
[GRAPHIC] [TIFF OMITTED] TR18JY97.184

where:

x=the annual mean; and

xq=the mean for calendar quarter q.

(d) The average of quarterly means must be rounded to the
nearest tenth (fractional values of 0.05 should be rounded up).
(e) The use of quarterly averages to compute the annual average
will not be necessary for monitoring or modeling data which results
in a complete record, i.e., 365 days per year.
(f) The expected annual mean is estimated as the average of
three or more annual means. This multi-year estimate, expressed in
g/m\3\, shall be rounded to the nearest integer for
comparison with the annual standard (fractional values of 0.5 should
be rounded up).

Example 4

Using Equation 4, the quarterly means are calculated for each
calendar quarter. If the quarterly means are 52.4, 75.3, 82.1, and
63.2 g/m \3\, then the annual mean is:

x = (1/4) x (52.4+75.3+82.1+63.2)= 68.25 or 68.3.

4.2 Adjustments for Non-scheduled Sampling Days. (a) An
adjustment in the calculation of the annual mean is needed if
sampling is performed on days in addition to the days specified by
the systematic sampling schedule. For the same reasons given in the
discussion of estimated exceedances, under section 3.2 of this
appendix, the quarterly averages would be calculated by using the
following equation:

Equation 6
[GRAPHIC] [TIFF OMITTED] TR18JY97.185

where:

xq=the quarterly mean concentration for quarter q, q=1,
2, 3, or 4;

xij=the ith concentration value recorded in stratum j;

kj=the number of actual samples in stratum j; and

mq=the number of strata with data in the quarter.

(b) If one sample value is recorded in each stratum, Equation 6
reduces to a simple arithmetic average of the observed values as
described by Equation 4.

Example 5

a. During one calendar quarter, 9 observations were recorded.
These samples were distributed among 7 sampling strata, with 3
observations in one stratum. The concentrations of the 3
observations in the single stratum were 202, 242, and 180
g/m\3\. The remaining 6 observed concentrations were 55,
68, 73, 92, 120, and 155 g/m\3\. Applying the weighting
factors specified in Equation 6, the quarterly mean is:

xq = (1/7) x [(1/3) x (202 + 242 + 180) + 155 + 68 +
73 + 92 + 120 + 155] = 110.1

b. Although 24-hour measurements are rounded to the nearest 10
g/m\3\ for determinations of exceedances of the 24-hour
standard, note that these values are rounded to the nearest 1
g/m\3\ for the calculation of means.
6. Appendix L is added to read as follows:

Appendix L to Part 50--Reference Method For the Determination of
Fine Particulate Matter as PM2.5 in the Atmosphere

1.0 Applicability.
1.1 This method provides for the measurement of the mass
concentration of fine particulate matter having an aerodynamic
diameter less than or equal to a nominal 2.5 micrometers
(PM2.5) in ambient air over a 24-hour period for purposes
of determining whether the primary and secondary national ambient
air quality standards for fine particulate matter specified in
Sec. 50.6 of this part are met. The measurement process is
considered to be nondestructive, and the PM2.5 sample
obtained can be subjected to subsequent physical or chemical
analyses. Quality assessment procedures are provided in part 58,
Appendix A of this chapter, and quality assurance guidance are
provided in references 1, 2, and 3 in section 13.0 of this appendix.
1.2 This method will be considered a reference method for
purposes of part 58 of this chapter only if:
(a) The associated sampler meets the requirements specified in
this appendix and the applicable requirements in part 53 of this
chapter, and
(b) The method and associated sampler have been designated as a
reference method in accordance with part 53 of this chapter.
1.3 PM2.5 samplers that meet nearly all
specifications set forth in this method but have minor deviations
and/or modifications of the reference method sampler will be
designated as ``Class I'' equivalent methods for PM2.5 in
accordance with part 53 of this chapter.
2.0 Principle.
2.1 An electrically powered air sampler draws ambient air at a
constant volumetric flow rate into a specially shaped inlet and
through an inertial particle size separator (impactor) where the
suspended particulate matter in the PM2.5 size range is
separated for collection on a polytetrafluoroethylene (PTFE) filter
over the specified sampling period. The air sampler and other
aspects of this reference method are specified either explicitly in
this appendix or generally with reference to other applicable
regulations or quality assurance guidance.
2.2 Each filter is weighed (after moisture and temperature
conditioning) before and after sample collection to determine the
net gain due to collected PM2.5. The total volume of air
sampled is determined by the sampler from the measured flow rate at
actual ambient temperature and pressure and the sampling time. The
mass concentration of PM2.5 in the ambient air is
computed as the total mass of collected particles in the
PM2.5 size range divided by the actual volume of air
sampled, and is expressed in micrograms per cubic meter of air
(g/m³).
3.0 PM2.5 Measurement Range.
3.1 Lower concentration limit. The lower detection limit of the
mass concentration measurement range is estimated to be
approximately 2 g/am³, based on noted mass
changes in field blanks in conjunction with the 24 m³
nominal total air sample volume specified for the 24-hour sample.
3.2 Upper concentration limit. The upper limit of the mass
concentration range is determined by the filter mass loading beyond
which the sampler can no longer maintain the operating flow rate
within specified limits due to increased pressure drop across the
loaded filter. This upper limit cannot be specified precisely
because it is a complex function of the ambient particle size
distribution and type, humidity, the individual filter used, the
capacity of the sampler flow rate control system, and perhaps other
factors. Nevertheless, all samplers are estimated to be capable of
measuring 24-hour PM2.5 mass concentrations of at least
200 g/m³ while maintaining the operating flow
rate within the specified limits.
3.3 Sample period. The required sample period for
PM2.5 concentration measurements by this method shall be
1,380 to 1500 minutes (23 to 25 hours). However, when a sample
period is less than 1,380 minutes, the measured concentration (as
determined by the collected PM2.5 mass divided by the
actual sampled air volume), multiplied by the actual number of
minutes in the sample period and divided by 1,440, may be used as if
it were a valid concentration measurement for the specific purpose
of determining a violation of the NAAQS. This value assumes

[[Page 38715]]

that the PM2.5 concentration is zero for the remaining
portion of the sample period and therefore represents the minimum
concentration that could have been measured for the full 24-hour
sample period. Accordingly, if the value thus calculated is high
enough to be an exceedance, such an exceedance would be a valid
exceedance for the sample period. When reported to AIRS, this data
value should receive a special code to identify it as not to be
commingled with normal concentration measurements or used for other
purposes.
4.0 Accuracy.
4.1 Because the size and volatility of the particles making up
ambient particulate matter vary over a wide range and the mass
concentration of particles varies with particle size, it is
difficult to define the accuracy of PM2.5 measurements in
an absolute sense. The accuracy of PM2.5 measurements is
therefore defined in a relative sense, referenced to measurements
provided by this reference method. Accordingly, accuracy shall be
defined as the degree of agreement between a subject field
PM2.5 sampler and a collocated PM2.5 reference
method audit sampler operating simultaneously at the monitoring site
location of the subject sampler and includes both random (precision)
and systematic (bias) errors. The requirements for this field
sampler audit procedure are set forth in part 58, Appendix A of this
chapter.
4.2 Measurement system bias. Results of collocated measurements
where the duplicate sampler is a reference method sampler are used
to assess a portion of the measurement system bias according to the
schedule and procedure specified in part 58, Appendix A of this
chapter.
4.3 Audits with reference method samplers to determine system
accuracy and bias. According to the schedule and procedure specified
in part 58, Appendix A of this chapter, a reference method sampler
is required to be located at each of selected PM2.5 SLAMS
sites as a duplicate sampler. The results from the primary sampler
and the duplicate reference method sampler are used to calculate
accuracy of the primary sampler on a quarterly basis, bias of the
primary sampler on an annual basis, and bias of a single reporting
organization on an annual basis. Reference 2 in section 13.0 of this
appendix provides additional information and guidance on these
reference method audits.
4.4 Flow rate accuracy and bias. Part 58, Appendix A of this
chapter requires that the flow rate accuracy and bias of individual
PM2.5 samplers used in SLAMS monitoring networks be
assessed periodically via audits of each sampler's operational flow
rate. In addition, part 58, Appendix A of this chapter requires that
flow rate bias for each reference and equivalent method operated by
each reporting organization be assessed quarterly and annually.
Reference 2 in section 13.0 of this appendix provides additional
information and guidance on flow rate accuracy audits and
calculations for accuracy and bias.
5.0 Precision. A data quality objective of 10 percent coefficient of
variation or better has been established for the operational
precision of PM2.5 monitoring data.
5.1 Tests to establish initial operational precision for each
reference method sampler are specified as a part of the requirements
for designation as a reference method under Sec. 53.58 of this
chapter.
5.2 Measurement System Precision. Collocated sampler results,
where the duplicate sampler is not a reference method sampler but is
a sampler of the same designated method as the primary sampler, are
used to assess measurement system precision according to the
schedule and procedure specified in part 58, Appendix A of this
chapter. Part 58, Appendix A of this chapter requires that these
collocated sampler measurements be used to calculate quarterly and
annual precision estimates for each primary sampler and for each
designated method employed by each reporting organization. Reference
2 in section 13.0 of this appendix provides additional information
and guidance on this requirement.
6.0 Filter for PM2.5 Sample Collection. Any filter
manufacturer or vendor who sells or offers to sell filters
specifically identified for use with this PM2.5 reference
method shall certify that the required number of filters from each
lot of filters offered for sale as such have been tested as
specified in this section 6.0 and meet all of the following design
and performance specifications.
6.1 Size. Circular, 46.2 mm diameter 0.25 mm.
6.2 Medium. Polytetrafluoroethylene (PTFE Teflon), with integral
support ring.
6.3 Support ring. Polymethylpentene (PMP) or equivalent inert
material, 0.38 0.04 mm thick, outer diameter 46.2 mm
0.25 mm, and width of 3.68 mm ( 0.00, -0.51
mm).
6.4 Pore size. 2 m as measured by ASTM F 316-94.
6.5 Filter thickness. 30 to 50 m.
6.6 Maximum pressure drop (clean filter). 30 cm H2O
column @ 16.67 L/min clean air flow.
6.7 Maximum moisture pickup. Not more than 10 g weight
increase after 24-hour exposure to air of 40 percent relative
humidity, relative to weight after 24-hour exposure to air of 35
percent relative humidity.
6.8 Collection efficiency. Greater than 99.7 percent, as
measured by the DOP test (ASTM D 2986-91) with 0.3 m
particles at the sampler's operating face velocity.
6.9 Filter weight stability. Filter weight loss shall be less
than 20 g, as measured in each of the following two tests
specified in sections 6.9.1 and 6.9.2 of this appendix. The
following conditions apply to both of these tests: Filter weight
loss shall be the average difference between the initial and the
final filter weights of a random sample of test filters selected
from each lot prior to sale. The number of filters tested shall be
not less than 0.1 percent of the filters of each manufacturing lot,
or 10 filters, whichever is greater. The filters shall be weighed
under laboratory conditions and shall have had no air sample passed
through them, i.e., filter blanks. Each test procedure must include
initial conditioning and weighing, the test, and final conditioning
and weighing. Conditioning and weighing shall be in accordance with
sections 8.0 through 8.2 of this appendix and general guidance
provided in reference 2 of section 13.0 of this appendix.
6.9.1 Test for loose, surface particle contamination. After the
initial weighing, install each test filter, in turn, in a filter
cassette (Figures L-27, L-28, and L-29 of this appendix) and drop
the cassette from a height of 25 cm to a flat hard surface, such as
a particle-free wood bench. Repeat two times, for a total of three
drop tests for each test filter. Remove the test filter from the
cassette and weigh the filter. The average change in weight must be
less than 20 g.
6.9.2 Test for temperature stability. After weighing each
filter, place the test filters in a drying oven set at 40 deg.C
2 deg.C for not less than 48 hours. Remove, condition,
and reweigh each test filter. The average change in weight must be
less than 20 g.
6.10 Alkalinity. Less than 25 microequivalents/gram of filter,
as measured by the guidance given in reference 2 in section 13.0 of
this appendix.
6.11 Supplemental requirements. Although not required for
determination of PM2.5 mass concentration under this
reference method, additional specifications for the filter must be
developed by users who intend to subject PM2.5 filter
samples to subsequent chemical analysis. These supplemental
specifications include background chemical contamination of the
filter and any other filter parameters that may be required by the
method of chemical analysis. All such supplemental filter
specifications must be compatible with and secondary to the primary
filter specifications given in this section 6.0 of this appendix.
7.0 PM2.5 Sampler.
7.1 Configuration. The sampler shall consist of a sample air
inlet, downtube, particle size separator (impactor), filter holder
assembly, air pump and flow rate control system, flow rate
measurement device, ambient and filter temperature monitoring
system, barometric pressure measurement system, timer, outdoor
environmental enclosure, and suitable mechanical, electrical, or

functional performance as specified in this section 7.0 of this
appendix. The performance specifications require that the sampler:
(a) Provide automatic control of sample volumetric flow rate and
other operational parameters.
(b) Monitor these operational parameters as well as ambient
temperature and pressure.
(c) Provide this information to the sampler operator at the end
of each sample period in digital form, as specified in Table L-1 of
section 7.4.19 of this appendix.
7.2 Nature of specifications. The PM2.5 sampler is
specified by a combination of design and performance requirements.
The sample inlet, downtube, particle size discriminator, filter
cassette, and the internal configuration of the filter holder
assembly are specified explicitly by design figures and associated
mechanical dimensions, tolerances, materials, surface finishes,
assembly instructions, and other necessary specifications. All other
aspects of the

[[Page 38716]]

sampler are specified by required operational function and
performance, and the design of these other aspects (including the
design of the lower portion of the filter holder assembly) is
optional, subject to acceptable operational performance. Test
procedures to demonstrate compliance with both the design and
performance requirements are set forth in subpart E of part 53 of
this chapter.
7.3 Design specifications. Except as indicated in this section
7.3 of this appendix, these components must be manufactured or
reproduced exactly as specified, in an ISO 9001-registered facility,
with registration initially approved and subsequently maintained
during the period of manufacture. See Sec. 53.1(t) of this chapter
for the definition of an ISO-registered facility. Minor
modifications or variances to one or more components that clearly
would not affect the aerodynamic performance of the inlet, downtube,
impactor, or filter cassette will be considered for specific
approval. Any such proposed modifications shall be described and
submitted to the EPA for specific individual acceptability either as
part of a reference or equivalent method application under part 53
of this chapter or in writing in advance of such an intended
application under part 53 of this chapter.
7.3.1 Sample inlet assembly. The sample inlet assembly,
consisting of the inlet, downtube, and impactor shall be configured
and assembled as indicated in Figure L-1 of this appendix and shall
meet all associated requirements. A portion of this assembly shall
also be subject to the maximum overall sampler leak rate
specification under section 7.4.6 of this appendix.
7.3.2 Inlet. The sample inlet shall be fabricated as indicated
in Figures L-2 through L-18 of this appendix and shall meet all
associated requirements.
7.3.3 Downtube. The downtube shall be fabricated as indicated in
Figure L-19 of this appendix and shall meet all associated
requirements.
7.3.4 Impactor.
7.3.4.1 The impactor (particle size separator) shall be
fabricated as indicated in Figures L-20 through L-24 of this
appendix and shall meet all associated requirements. Following the
manufacture and finishing of each upper impactor housing (Figure L-
21 of this appendix), the dimension of the impaction jet must be
verified by the manufacturer using Class ZZ go/no-go plug gauges
that are traceable to NIST.
7.3.4.2 Impactor filter specifications:
(a) Size. Circular, 35 to 37 mm diameter.
(b) Medium. Borosilicate glass fiber, without binder.
(c) Pore size. 1 to 1.5 micrometer, as measured by ASTM F 316-
80.
(d) Thickness. 300 to 500 micrometers.
7.3.4.3 Impactor oil specifications:
(a) Composition. Tetramethyltetraphenyltrisiloxane, single-
compound diffusion oil.
(b) Vapor pressure. Maximum 2 x 10^-8 mm Hg at 25
deg.C.
(c) Viscosity. 36 to 40 centistokes at 25 deg.C.
(d) Density. 1.06 to 1.07 g/cm³ at 25 deg.C.
(e) Quantity. 1 mL 0.1 mL.
7.3.5 Filter holder assembly. The sampler shall have a sample
filter holder assembly to adapt and seal to the down tube and to
hold and seal the specified filter, under section 6.0 of this
appendix, in the sample air stream in a horizontal position below
the downtube such that the sample air passes downward through the
filter at a uniform face velocity. The upper portion of this
assembly shall be fabricated as indicated in Figures L-25 and L-26
of this appendix and shall accept and seal with the filter cassette,
which shall be fabricated as indicated in Figures L-27 through L-29
of this appendix.
(a) The lower portion of the filter holder assembly shall be of
a design and construction that:
(1) Mates with the upper portion of the assembly to complete the
filter holder assembly,
(2) Completes both the external air seal and the internal filter
cassette seal such that all seals are reliable over repeated filter
changings, and
(3) Facilitates repeated changing of the filter cassette by the
sampler operator.
(b) Leak-test performance requirements for the filter holder
assembly are included in section 7.4.6 of this appendix.
(c) If additional or multiple filters are stored in the sampler
as part of an automatic sequential sample capability, all such
filters, unless they are currently and directly installed in a
sampling channel or sampling configuration (either active or
inactive), shall be covered or (preferably) sealed in such a way as
to:
(1) Preclude significant exposure of the filter to possible
contamination or accumulation of dust, insects, or other material
that may be present in the ambient air, sampler, or sampler
ventilation air during storage periods either before or after
sampling; and
(2) To minimize loss of volatile or semi-volatile PM sample
components during storage of the filter following the sample period.
7.3.6 Flow rate measurement adapter. A flow rate measurement
adapter as specified in Figure L-30 of this appendix shall be
furnished with each sampler.
7.3.7 Surface finish. All internal surfaces exposed to sample
air prior to the filter shall be treated electrolytically in a
sulfuric acid bath to produce a clear, uniform anodized surface
finish of not less than 1000 mg/ft² (1.08 mg/
cm²) in accordance with military standard specification
(mil. spec.) 8625F, Type II, Class 1 in reference 4 of section 13.0
of this appendix. This anodic surface coating shall not be dyed or
pigmented. Following anodization, the surfaces shall be sealed by
immersion in boiling deionized water for not less than 15 minutes.
Section 53.51(d)(2) of this chapter should also be consulted.
7.3.8 Sampling height. The sampler shall be equipped with legs,
a stand, or other means to maintain the sampler in a stable, upright
position and such that the center of the sample air entrance to the
inlet, during sample collection, is maintained in a horizontal plane
and is 2.0 0.2 meters above the floor or other
horizontal supporting surface. Suitable bolt holes, brackets, tie-
downs, or other means should be provided to facilitate mechanically
securing the sample to the supporting surface to prevent toppling of
the sampler due to wind.
7.4 Performance specifications.
7.4.1 Sample flow rate. Proper operation of the impactor
requires that specific air velocities be maintained through the
device. Therefore, the design sample air flow rate through the inlet
shall be 16.67 L/min (1.000 m³/hour) measured as actual
volumetric flow rate at the temperature and pressure of the sample
air entering the inlet.
7.4.2 Sample air flow rate control system. The sampler shall
have a sample air flow rate control system which shall be capable of
providing a sample air volumetric flow rate within the specified
range, under section 7.4.1 of this appendix, for the specified
filter, under section 6.0 of this appendix, at any atmospheric
conditions specified, under section 7.4.7 of this appendix, at a
filter pressure drop equal to that of a clean filter plus up to 75
cm water column (55 mm Hg), and over the specified range of supply
line voltage, under section 7.4.15.1 of this appendix. This flow
control system shall allow for operator adjustment of the
operational flow rate of the sampler over a range of at least
15 percent of the flow rate specified in section 7.4.1
of this appendix.
7.4.3 Sample flow rate regulation. The sample flow rate shall be
regulated such that for the specified filter, under section 6.0 of
this appendix, at any atmospheric conditions specified, under
section 7.4.7 of this appendix, at a filter pressure drop equal to
that of a clean filter plus up to 75 cm water column (55 mm Hg), and
over the specified range of supply line voltage, under section
7.4.15.1 of this appendix, the flow rate is regulated as follows:
7.4.3.1 The volumetric flow rate, measured or averaged over
intervals of not more than 5 minutes over a 24-hour period, shall
not vary more than 5 percent from the specified 16.67 L/
min flow rate over the entire sample period.
7.4.3.2 The coefficient of variation (sample standard deviation
divided by the mean) of the flow rate, measured over a 24-hour
period, shall not be greater than 2 percent.
7.4.3.3 The amplitude of short-term flow rate pulsations, such
as may originate from some types of vacuum pumps, shall be
attenuated such that they do not cause significant flow measurement
error or affect the collection of particles on the particle
collection filter.
7.4.4 Flow rate cut off. The sampler's sample air flow rate
control system shall terminate sample collection and stop all sample
flow for the remainder of the sample period in the event that the
sample flow rate deviates by more than 10 percent from the sampler
design flow rate specified in section 7.4.1 of this appendix for
more than 60 seconds. However, this sampler cut-off provision shall
not apply during periods when the sampler is inoperative due to a
temporary power interruption, and the elapsed time of the
inoperative period shall not be included in the total sample time
measured and reported by the sampler, under section 7.4.13 of this
appendix.
7.4.5 Flow rate measurement.
7.4.5.1 The sampler shall provide a means to measure and
indicate the instantaneous sample air flow rate, which shall be
measured as volumetric flow rate at the

[[Page 38717]]

temperature and pressure of the sample air entering the inlet, with
an accuracy of 2 percent. The measured flow rate shall
be available for display to the sampler operator at any time in
either sampling or standby modes, and the measurement shall be
updated at least every 30 seconds. The sampler shall also provide a
simple means by which the sampler operator can manually start the
sample flow temporarily during non-sampling modes of operation, for
the purpose of checking the sample flow rate or the flow rate
measurement system.
7.4.5.2 During each sample period, the sampler's flow rate
measurement system shall automatically monitor the sample volumetric
flow rate, obtaining flow rate measurements at intervals of not
greater than 30 seconds.
(a) Using these interval flow rate measurements, the sampler
shall determine or calculate the following flow-related parameters,
scaled in the specified engineering units:
(1) The instantaneous or interval-average flow rate, in L/min.
(2) The value of the average sample flow rate for the sample
period, in L/min.
(3) The value of the coefficient of variation (sample standard
deviation divided by the average) of the sample flow rate for the
sample period, in percent.
(4) The occurrence of any time interval during the sample period
in which the measured sample flow rate exceeds a range of
5 percent of the average flow rate for the sample period
for more than 5 minutes, in which case a warning flag indicator
shall be set.
(5) The value of the integrated total sample volume for the
sample period, in m³.
(b) Determination or calculation of these values shall properly
exclude periods when the sampler is inoperative due to temporary
interruption of electrical power, under section 7.4.13 of this
appendix, or flow rate cut off, under section 7.4.4 of this
appendix.
(c) These parameters shall be accessible to the sampler operator
as specified in Table L-1 of section 7.4.19 of this appendix. In
addition, it is strongly encouraged that the flow rate for each 5-
minute interval during the sample period be available to the
operator following the end of the sample period.
7.4.6 Leak test capability.
7.4.6.1 External leakage. The sampler shall include an external
air leak-test capability consisting of components, accessory
hardware, operator interface controls, a written procedure in the
associated Operation/Instruction Manual, under section 7.4.18 of
this appendix, and all other necessary functional capability to
permit and facilitate the sampler operator to conveniently carry out
a leak test of the sampler at a field monitoring site without
additional equipment. The sampler components to be subjected to this
leak test include all components and their interconnections in which
external air leakage would or could cause an error in the sampler's
measurement of the total volume of sample air that passes through
the sample filter.
(a) The suggested technique for the operator to use for this
leak test is as follows:
(1) Remove the sampler inlet and installs the flow rate
measurement adapter supplied with the sampler, under section 7.3.6
of this appendix.
(2) Close the valve on the flow rate measurement adapter and use
the sampler air pump to draw a partial vacuum in the sampler,
including (at least) the impactor, filter holder assembly (filter in
place), flow measurement device, and interconnections between these
devices, of at least 55 mm Hg (75 cm water column), measured at a
location downstream of the filter holder assembly.
(3) Plug the flow system downstream of these components to
isolate the components under vacuum from the pump, such as with a
built-in valve.
(4) Stop the pump.
(5) Measure the trapped vacuum in the sampler with a built-in
pressure measuring device.
(6) (i) Measure the vacuum in the sampler with the built-in
pressure measuring device again at a later time at least 10 minutes
after the first pressure measurement.
(ii) Caution: Following completion of the test, the adaptor
valve should be opened slowly to limit the flow rate of air into the
sampler. Excessive air flow rate may blow oil out of the impactor.
(7) Upon completion of the test, open the adaptor valve, remove
the adaptor and plugs, and restore the sampler to the normal
operating configuration.
(b) The associated leak test procedure shall require that for
successful passage of this test, the difference between the two
pressure measurements shall not be greater than the number of mm of
Hg specified for the sampler by the manufacturer, based on the
actual internal volume of the sampler, that indicates a leak of less
than 80 mL/min.
(c) Variations of the suggested technique or an alternative
external leak test technique may be required for samplers whose
design or configuration would make the suggested technique
impossible or impractical. The specific proposed external leak test
procedure, or particularly an alternative leak test technique,
proposed for a particular candidate sampler may be described and
submitted to the EPA for specific individual acceptability either as
part of a reference or equivalent method application under part 53
of this chapter or in writing in advance of such an intended
application under part 53 of this chapter.
7.4.6.2 Internal, filter bypass leakage. The sampler shall
include an internal, filter bypass leak-check capability consisting
of components, accessory hardware, operator interface controls, a
written procedure in the Operation/Instruction Manual, and all other
necessary functional capability to permit and facilitate the sampler
operator to conveniently carry out a test for internal filter bypass
leakage in the sampler at a field monitoring site without additional
equipment. The purpose of the test is to determine that any portion
of the sample flow rate that leaks past the sample filter without
passing through the filter is insignificant relative to the design
flow rate for the sampler.
(a) The suggested technique for the operator to use for this
leak test is as follows:
(1) Carry out an external leak test as provided under section
7.4.6.1 of this appendix which indicates successful passage of the
prescribed external leak test.
(2) Install a flow-impervious membrane material in the filter
cassette, either with or without a filter, as appropriate, which
effectively prevents air flow through the filter.
(3) Use the sampler air pump to draw a partial vacuum in the
sampler, downstream of the filter holder assembly, of at least 55 mm
Hg (75 cm water column).
(4) Plug the flow system downstream of the filter holder to
isolate the components under vacuum from the pump, such as with a
built-in valve.
(5) Stop the pump.
(6) Measure the trapped vacuum in the sampler with a built-in
pressure measuring device.
(7) Measure the vacuum in the sampler with the built-in pressure
measuring device again at a later time at least 10 minutes after the
first pressure measurement.
(8) Remove the flow plug and membrane and restore the sampler to
the normal operating configuration.
(b) The associated leak test procedure shall require that for
successful passage of this test, the difference between the two
pressure measurements shall not be greater than the number of mm of
Hg specified for the sampler by the manufacturer, based on the
actual internal volume of the portion of the sampler under vacuum,
that indicates a leak of less than 80 mL/min.
(c) Variations of the suggested technique or an alternative
internal, filter bypass leak test technique may be required for
samplers whose design or configuration would make the suggested
technique impossible or impractical. The specific proposed internal
leak test procedure, or particularly an alternative internal leak
test technique proposed for a particular candidate sampler may be
described and submitted to the EPA for specific individual
acceptability either as part of a reference or equivalent method
application under part 53 of this chapter or in writing in advance
of such intended application under part 53 of this chapter.
7.4.7 Range of operational conditions. The sampler is required
to operate properly and meet all requirements specified in this
appendix over the following operational ranges.
7.4.7.1 Ambient temperature. -30 to +45 deg.C (Note: Although
for practical reasons, the temperature range over which samplers are
required to be tested under part 53 of this chapter is -20 to +40
deg.C, the sampler shall be designed to operate properly over this
wider temperature range.).
7.4.7.2 Ambient relative humidity. 0 to 100 percent.
7.4.7.3 Barometric pressure range. 600 to 800 mm Hg.
7.4.8 Ambient temperature sensor. The sampler shall have
capability to measure the temperature of the ambient air surrounding
the sampler over the range of -30 to +45 deg.C, with a resolution
of 0.1 deg.C and accuracy of 2.0 deg.C, referenced as
described in reference 3 in section 13.0 of this appendix, with and
without maximum solar insolation.

[[Page 38718]]

7.4.8.1 The ambient temperature sensor shall be mounted external
to the sampler enclosure and shall have a passive, naturally
ventilated sun shield. The sensor shall be located such that the
entire sun shield is at least 5 cm above the horizontal plane of the
sampler case or enclosure (disregarding the inlet and downtube) and
external to the vertical plane of the nearest side or protuberance
of the sampler case or enclosure. The maximum temperature
measurement error of the ambient temperature measurement system
shall be less than 1.6 deg.C at 1 m/s wind speed and 1000 W/m2
solar radiation intensity.
7.4.8.2 The ambient temperature sensor shall be of such a design
and mounted in such a way as to facilitate its convenient
dismounting and immersion in a liquid for calibration and comparison
to the filter temperature sensor, under section 7.4.11 of this
appendix.
7.4.8.3 This ambient temperature measurement shall be updated at
least every 30 seconds during both sampling and standby (non-
sampling) modes of operation. A visual indication of the current
(most recent) value of the ambient temperature measurement, updated
at least every 30 seconds, shall be available to the sampler
operator during both sampling and standby (non-sampling) modes of
operation, as specified in Table L-1 of section 7.4.19 of this
appendix.
7.4.8.4 This ambient temperature measurement shall be used for
the purpose of monitoring filter temperature deviation from ambient
temperature, as required by section 7.4.11 of this appendix, and may
be used for purposes of effecting filter temperature control, under
section 7.4.10 of this appendix, or computation of volumetric flow
rate, under sections 7.4.1 to 7.4.5 of this appendix, if
appropriate.
7.4.8.5 Following the end of each sample period, the sampler
shall report the maximum, minimum, and average temperature for the
sample period, as specified in Table L-1 of section 7.4.19 of this
appendix.
7.4.9 Ambient barometric sensor. The sampler shall have
capability to measure the barometric pressure of the air surrounding
the sampler over a range of 600 to 800 mm Hg referenced as described
in reference 3 in section 13.0 of this appendix; also see part 53,
subpart E of this chapter. This barometric pressure measurement
shall have a resolution of 5 mm Hg and an accuracy of 10
mm Hg and shall be updated at least every 30 seconds. A visual
indication of the value of the current (most recent) barometric
pressure measurement, updated at least every 30 seconds, shall be
available to the sampler operator during both sampling and standby
(non-sampling) modes of operation, as specified in Table L-1 of
section 7.4.19 of this appendix. This barometric pressure
measurement may be used for purposes of computation of volumetric
flow rate, under sections 7.4.1 to 7.4.5 of this appendix, if
appropriate. Following the end of a sample period, the sampler shall
report the maximum, minimum, and mean barometric pressures for the
sample period, as specified in Table L-1 of section 7.4.19 of this
appendix.
7.4.10 Filter temperature control (sampling and post-sampling).
The sampler shall provide a means to limit the temperature rise of
the sample filter (all sample filters for sequential samplers), from
insolation and other sources, to no more 5 deg.C above the
temperature of the ambient air surrounding the sampler, during both
sampling and post-sampling periods of operation. The post-sampling
period is the non-sampling period between the end of the active
sampling period and the time of retrieval of the sample filter by
the sampler operator.
7.4.11 Filter temperature sensor(s).
7.4.11.1 The sampler shall have the capability to monitor the
temperature of the sample filter (all sample filters for sequential
samplers) over the range of -30 to +45 deg.C during both sampling
and non-sampling periods. While the exact location of this
temperature sensor is not explicitly specified, the filter
temperature measurement system must demonstrate agreement, within 1
deg.C, with a test temperature sensor located within 1 cm of the
center of the filter downstream of the filter during both sampling
and non-sampling modes, as specified in the filter temperature
measurement test described in part 53, subpart E of this chapter.
This filter temperature measurement shall have a resolution of 0.1
deg.C and accuracy of 1.0 deg.C, referenced as
described in reference 3 in section 13.0 of this appendix. This
temperature sensor shall be of such a design and mounted in such a
way as to facilitate its reasonably convenient dismounting and
immersion in a liquid for calibration and comparison to the ambient
temperature sensor under section 7.4.8 of this appendix.
7.4.11.2 The filter temperature measurement shall be updated at
least every 30 seconds during both sampling and standby (non-
sampling) modes of operation. A visual indication of the current
(most recent) value of the filter temperature measurement, updated
at least every 30 seconds, shall be available to the sampler
operator during both sampling and standby (non-sampling) modes of
operation, as specified in Table L-1 of section 7.4.19 of this
appendix.
7.4.11.3 For sequential samplers, the temperature of each filter
shall be measured individually unless it can be shown, as specified
in the filter temperature measurement test described in Sec. 53.57
of this chapter, that the temperature of each filter can be
represented by fewer temperature sensors.
7.4.11.4 The sampler shall also provide a warning flag indicator
following any occurrence in which the filter temperature (any filter
temperature for sequential samplers) exceeds the ambient temperature
by more than 5 deg.C for more than 30 consecutive minutes during
either the sampling or post-sampling periods of operation, as
specified in Table L-1 of section 7.4.19 of this appendix, under
section 10.12 of this appendix, regarding sample validity when a
warning flag occurs. It is further recommended (not required) that
the sampler be capable of recording the maximum differential between
the measured filter temperature and the ambient temperature and its
time and date of occurrence during both sampling and post-sampling
(non-sampling) modes of operation and providing for those data to be
accessible to the sampler operator following the end of the sample
period, as suggested in Table L-1 of section 7.4.19 of this
appendix.
7.4.12 Clock/timer system.
(a) The sampler shall have a programmable real-time clock
timing/control system that:
(1) Is capable of maintaining local time and date, including
year, month, day-of-month, hour, minute, and second to an accuracy
of 1.0 minute per month.
(2) Provides a visual indication of the current system time,
including year, month, day-of-month, hour, and minute, updated at
least each minute, for operator verification.
(3) Provides appropriate operator controls for setting the
correct local time and date.
(4) Is capable of starting the sample collection period and
sample air flow at a specific, operator-settable time and date, and
stopping the sample air flow and terminating the sampler collection
period 24 hours (1440 minutes) later, or at a specific, operator-
settable time and date.
(b) These start and stop times shall be readily settable by the
sampler operator to within 1.0 minute. The system shall
provide a visual indication of the current start and stop time
settings, readable to 1.0 minute, for verification by
the operator, and the start and stop times shall also be available
via the data output port, as specified in Table L-1 of section
7.4.19 of this appendix. Upon execution of a programmed sample
period start, the sampler shall automatically reset all sample
period information and warning flag indications pertaining to a
previous sample period. Refer also to section 7.4.15.4 of this
appendix regarding retention of current date and time and programmed
start and stop times during a temporary electrical power
interruption.
7.4.13 Sample time determination. The sampler shall be capable
of determining the elapsed sample collection time for each
PM2.5 sample, accurate to within 1.0 minute,
measured as the time between the start of the sampling period, under
section 7.4.12 of this appendix and the termination of the sample
period, under section 7.4.12 of this appendix or section 7.4.4 of
this appendix. This elapsed sample time shall not include periods
when the sampler is inoperative due to a temporary interruption of
electrical power, under section 7.4.15.4 of this appendix. In the
event that the elapsed sample time determined for the sample period
is not within the range specified for the required sample period in
section 3.3 of this appendix, the sampler shall set a warning flag
indicator. The date and time of the start of the sample period, the
value of the elapsed sample time for the sample period, and the flag
indicator status shall be available to the sampler operator
following the end of the sample period, as specified in Table L-1 of
section 7.4.19 of this appendix.
7.4.14 Outdoor environmental enclosure. The sampler shall have
an outdoor enclosure (or enclosures) suitable to protect the filter
and other non-weatherproof components of the sampler from
precipitation, wind, dust, extremes of temperature and humidity; to
help maintain temperature control of the

[[Page 38719]]

filter (or filters, for sequential samplers); and to provide
reasonable security for sampler components and settings.
7.4.15 Electrical power supply.
7.4.15.1 The sampler shall be operable and function as specified
herein when operated on an electrical power supply voltage of 105 to
125 volts AC (RMS) at a frequency of 59 to 61 Hz. Optional operation
as specified at additional power supply voltages and/or frequencies
shall not be precluded by this requirement.
7.4.15.2 The design and construction of the sampler shall comply
with all applicable National Electrical Code and Underwriters
Laboratories electrical safety requirements.
7.4.15.3 The design of all electrical and electronic controls
shall be such as to provide reasonable resistance to interference or
malfunction from ordinary or typical levels of stray electromagnetic
fields (EMF) as may be found at various monitoring sites and from
typical levels of electrical transients or electronic noise as may
often or occasionally be present on various electrical power lines.
7.4.15.4 In the event of temporary loss of electrical supply
power to the sampler, the sampler shall not be required to sample or
provide other specified functions during such loss of power, except
that the internal clock/timer system shall maintain its local time
and date setting within 1 minute per week, and the
sampler shall retain all other time and programmable settings and
all data required to be available to the sampler operator following
each sample period for at least 7 days without electrical supply
power. When electrical power is absent at the operator-set time for
starting a sample period or is interrupted during a sample period,
the sampler shall automatically start or resume sampling when
electrical power is restored, if such restoration of power occurs
before the operator-set stop time for the sample period.
7.4.15.5 The sampler shall have the capability to record and
retain a record of the year, month, day-of-month, hour, and minute
of the start of each power interruption of more than 1 minute
duration, up to 10 such power interruptions per sample period. (More
than 10 such power interruptions shall invalidate the sample, except
where an exceedance is measured, under section 3.3 of this
appendix.) The sampler shall provide for these power interruption
data to be available to the sampler operator following the end of
the sample period, as specified in Table L-1 of section 7.4.19 of
this appendix.
7.4.16 Control devices and operator interface. The sampler shall
have mechanical, electrical, or electronic controls, control
devices, electrical or electronic circuits as necessary to provide
the timing, flow rate measurement and control, temperature control,
data storage and computation, operator interface, and other
functions specified. Operator-accessible controls, data displays,
and interface devices shall be designed to be simple,
straightforward, reliable, and easy to learn, read, and operate
under field conditions. The sampler shall have provision for
operator input and storage of up to 64 characters of numeric (or
alphanumeric) data for purposes of site, sampler, and sample
identification. This information shall be available to the sampler
operator for verification and change and for output via the data
output port along with other data following the end of a sample
period, as specified in Table L-1 of section 7.4.19 of this
appendix. All data required to be available to the operator
following a sample collection period or obtained during standby mode
in a post-sampling period shall be retained by the sampler until
reset, either manually by the operator or automatically by the
sampler upon initiation of a new sample collection period.
7.4.17 Data output port requirement. The sampler shall have a
standard RS-232C data output connection through which digital data
may be exported to an external data storage or transmission device.
All information which is required to be available at the end of each
sample period shall be accessible through this data output
connection. The information that shall be accessible though this
output port is summarized in Table L-1 of section 7.4.19 of this
appendix. Since no specific format for the output data is provided,
the sampler manufacturer or vendor shall make available to sampler
purchasers appropriate computer software capable of receiving
exported sampler data and correctly translating the data into a
standard spreadsheet format and optionally any other formats as may
be useful to sampler users. This requirement shall not preclude the
sampler from offering other types of output connections in addition
to the required RS-232C port.
7.4.18 Operation/instruction manual. The sampler shall include
an associated comprehensive operation or instruction manual, as
required by part 53 of this chapter, which includes detailed
operating instructions on the setup, operation, calibration, and
maintenance of the sampler. This manual shall provide complete and
detailed descriptions of the operational and calibration procedures
prescribed for field use of the sampler and all instruments utilized
as part of this reference method. The manual shall include adequate
warning of potential safety hazards that may result from normal use
or malfunction of the method and a description of necessary safety
precautions. The manual shall also include a clear description of
all procedures pertaining to installation, operation, periodic and
corrective maintenance, and troubleshooting, and shall include parts
identification diagrams.
7.4.19 Data reporting requirements. The various information that
the sampler is required to provide and how it is to be provided is
summarized in the following Table L-1.

Table L-1.--Summary of Information To Be Provided By the Sampler
----------------------------------------------------------------------------------------------------------------------------------------------
Availability Format
Appendix L section ---------------------------------------------------------------------------------------
Information to be provided reference End of Visual
Anytime¹ period² display³ Data output⁴ Digital reading⁵ Units
----------------------------------------------------------------------------------------------------------------------------------------------
Flow rate, 30-second maximum 7.4.5.1............ ............ * XX.X............... L/min
interval.
Flow rate, average for the sample 7.4.5.2............ * * XX.X............... L/min
period.
Flow rate, CV, for sample period. 7.4.5.2............ * * XX.X............... %
Flow rate, 5-min. average out of 7.4.5.2............ On/Off............. ...................
spec. (FLAG⁶).
Sample volume, total............. 7.4.5.2............ * XX.X............... m³
Temperature, ambient, 30-second 7.4.8.............. ............ ............ XX.X............... deg.C
interval.
Temperature, ambient, min., max., 7.4.8.............. * XX.X............... deg.C
average for the sample period.
Baro pressure, ambient, 30-second 7.4.9.............. ............ ............ XXX................ mm Hg
interval.

[[Page 38720]]

Baro pressure, ambient, min., 7.4.9.............. * XXX................ mm Hg
max., average for the sample
period.
Filter temperature, 30-second 7.4.11............. ............ ............ XX.X............... deg.C
interval.
Filter temperature differential, 7.4.11............. * On/Off............. ...................
30-second interval, out of spec.
(FLAG⁶).
Filter temperature, maximum 7.4.11............. * * * * X.X, YY/MM/DD HH:mm deg.C, Yr./Mon./
differential from ambient, date, Day Hrs. min
time of occurrence.
Date and time.................... 7.4.12............. ............ ............ YY/MM/DD HH:mm..... Yr./Mon./Day Hrs.
min
Sample start and stop time 7.4.12............. YY/MM/DD HH:mm..... Yr./Mon./Day Hrs.
settings. min
Sample period start time......... 7.4.12............. ............ YYYY/MM/DD HH:mm... Yr./Mon./Day Hrs.
min
Elapsed sample time.............. 7.4.13............. * HH:mm.............. Hrs. min
Elapsed sample time, out of spec. 7.4.13............. ............ On/Off............. ...................
(FLAG⁶).
Power interruptions >1 min., 7.4.15.5........... * * 1HH:mm, 2HH:mm, etc Hrs. min
start time of first 10. ....
User-entered information, such as 7.4.16............. As entered......... ...................
sampler and site identification.
----------------------------------------------------------------------------------------------------------------------------------------------

Provision of this information is required.
Provision of this information is optional. If information related to the entire sample period is optionally provided prior to the
end of the sample period, the value provided should be the value calculated for the portion of the sampler period completed up to the
time the information is provided.
Indicates that this information is also required to be provided to the AIRS data bank; see Sec. Sec. 58.26 and 58.35 of this chapter.

¹ Information is required to be available to the operator at any time the sampler is operating, whether sampling or not.
² Information relates to the entire sampler period and must be provided following the end of the sample period until reset
manually by the operator or automatically by the sampler upon the start of a new sample period.
³ Information shall be available to the operator visually.
⁴ Information is to be available as digital data at the sampler's data output port specified in section 7.4.16 of this
appendix following the end of the sample period until reset manually by the operator or automatically by the sampler upon
the start of a new sample period.
⁵ Digital readings, both visual and data output, shall have not less than the number of significant digits and
resolution specified.
⁶ Flag warnings may be displayed to the operator by a single-flag indicator or each flag may be displayed individually.
Only a set (on) flag warning must be indicated; an off (unset) flag may be indicated by the absence of a flag warning.
Sampler users should refer to section 10.12 of this appendix regarding the validity of samples for which the sampler provided an
associated flag warning. 8.0 Filter Weighing. See reference 2 in section 13.0 of this appendix, for additional, more detailed guidance.
8.1 Analytical balance. The analytical balance used to weigh
filters must be suitable for weighing the type and size of filters
specified, under section 6.0 of this appendix, and have a
readability of 1 g. The balance shall be
calibrated as specified by the manufacturer at installation and
recalibrated immediately prior to each weighing session. See
reference 2 in section 13.0 of this appendix for additional
guidance.
8.2 Filter conditioning. All sample filters used shall be
conditioned immediately before both the pre- and post-sampling
weighings as specified below. See reference 2 in section 13.0 of
this appendix for additional guidance.
8.2.1 Mean temperature. 20 - 23 deg.C.
8.2.2 Temperature control. 2 deg.C over 24 hours.
8.2.3 Mean humidity. Generally, 30-40 percent relative humidity;
however, where it can be shown that the mean ambient relative
humidity during sampling is less than 30 percent, conditioning is
permissible at a mean relative humidity within 5
relative humidity percent of the mean ambient relative humidity
during sampling, but not less than 20 percent.
8.2.4 Humidity control. 5 relative humidity percent
over 24 hours.
8.2.5 Conditioning time. Not less than 24 hours.
8.3 Weighing procedure.
8.3.1 New filters should be placed in the conditioning
environment immediately upon arrival and stored there until the pre-
sampling weighing. See reference 2 in section 13.0 of this appendix
for additional guidance.
8.3.2 The analytical balance shall be located in the same
controlled environment in which the filters are conditioned. The
filters shall be weighed immediately following the conditioning
period without intermediate or transient exposure to other
conditions or environments.
8.3.3 Filters must be conditioned at the same conditions
(humidity within 5 relative humidity percent) before
both the pre- and post-sampling weighings.
8.3.4 Both the pre- and post-sampling weighings should be
carried out on the same analytical balance, using an effective
technique to neutralize static charges on the filter, under
reference 2 in section 13.0 of this appendix. If possible, both
weighings should be carried out by the same analyst.
8.3.5 The pre-sampling (tare) weighing shall be within 30 days
of the sampling period.
8.3.6 The post-sampling conditioning and weighing shall be
completed within 240 hours (10 days) after the end of the sample
period, unless the filter sample is maintained at 4 deg.C or less
during the entire time between retrieval from the sampler and the
start of the conditioning, in which case the period shall

[[Page 38721]]

not exceed 30 days. Reference 2 in section 13.0 of this appendix has
additional guidance on transport of cooled filters.
8.3.7 Filter blanks.
8.3.7.1 New field blank filters shall be weighed along with the
pre-sampling (tare) weighing of each lot of PM2.5
filters. These blank filters shall be transported to the sampling
site, installed in the sampler, retrieved from the sampler without
sampling, and reweighed as a quality control check.
8.3.7.2 New laboratory blank filters shall be weighed along with
the pre-sampling (tare) weighing of each set of PM2.5
filters. These laboratory blank filters should remain in the
laboratory in protective containers during the field sampling and
should be reweighed as a quality control check.
8.3.8 Additional guidance for proper filter weighing and related
quality assurance activities is provided in reference 2 in section
13.0 of this appendix.
9.0 Calibration. Reference 2 in section 13.0 of this appendix
contains additional guidance.
9.1 General requirements.
9.1.1 Multipoint calibration and single-point verification of
the sampler's flow rate measurement device must be performed
periodically to establish and maintain traceability of subsequent
flow measurements to a flow rate standard.
9.1.2 An authoritative flow rate standard shall be used for
calibrating or verifying the sampler's flow rate measurement device
with an accuracy of 2 percent. The flow rate standard
shall be a separate, stand-alone device designed to connect to the
flow rate measurement adapter, Figure L-30 of this appendix. This
flow rate standard must have its own certification and be traceable
to a National Institute of Standards and Technology (NIST) primary
standard for volume or flow rate. If adjustments to the sampler's
flow rate measurement system calibration are to be made in
conjunction with an audit of the sampler's flow measurement system,
such adjustments shall be made following the audit. Reference 2 in
section 13.0 of this appendix contains additional guidance.
9.1.3 The sampler's flow rate measurement device shall be re-
calibrated after electromechanical maintenance or transport of the
sampler.
9.2 Flow rate calibration/verification procedure.
9.2.1 PM2.5 samplers may employ various types of flow
control and flow measurement devices. The specific procedure used
for calibration or verification of the flow rate measurement device
will vary depending on the type of flow rate controller and flow
rate measurement employed. Calibration shall be in terms of actual
ambient volumetric flow rates (Q^a), measured at the
sampler's inlet downtube. The generic procedure given here serves to
illustrate the general steps involved in the calibration of a
PM2.5 sampler. The sampler operation/instruction manual
required under section 7.4.18 of this appendix and the Quality
Assurance Handbook in reference 2 in section 13.0 of this appendix
provide more specific and detailed guidance for calibration.
9.2.2 The flow rate standard used for flow rate calibration
shall have its own certification and be traceable to a NIST primary
standard for volume or flow rate. A calibration relationship for the
flow rate standard, e.g., an equation, curve, or family of curves
relating actual flow rate (Qa) to the flow rate indicator
reading, shall be established that is accurate to within 2 percent
over the expected range of ambient temperatures and pressures at
which the flow rate standard may be used. The flow rate standard
must be re-calibrated or re-verified at least annually.
9.2.3 The sampler flow rate measurement device shall be
calibrated or verified by removing the sampler inlet and connecting
the flow rate standard to the sampler's downtube in accordance with
the operation/instruction manual, such that the flow rate standard
accurately measures the sampler's flow rate. The sampler operator
shall first carry out a sampler leak check and confirm that the
sampler passes the leak test and then verify that no leaks exist
between the flow rate standard and the sampler.
9.2.4 The calibration relationship between the flow rate (in
actual L/min) indicated by the flow rate standard and by the
sampler's flow rate measurement device shall be established or
verified in accordance with the sampler operation/instruction
manual. Temperature and pressure corrections to the flow rate
indicated by the flow rate standard may be required for certain
types of flow rate standards. Calibration of the sampler's flow rate
measurement device shall consist of at least three separate flow
rate measurements (multipoint calibration) evenly spaced within the
range of -10 percent to +10 percent of the sampler's operational
flow rate, section 7.4.1 of this appendix. Verification of the
sampler's flow rate shall consist of one flow rate measurement at
the sampler's operational flow rate. The sampler operation/
instruction manual and reference 2 in section 13.0 of this appendix
provide additional guidance.
9.2.5 If during a flow rate verification the reading of the
sampler's flow rate indicator or measurement device differs by
2 percent or more from the flow rate measured by the
flow rate standard, a new multipoint calibration shall be performed
and the flow rate verification must then be repeated.
9.2.6 Following the calibration or verification, the flow rate
standard shall be removed from the sampler and the sampler inlet
shall be reinstalled. Then the sampler's normal operating flow rate
(in L/min) shall be determined with a clean filter in place. If the
flow rate indicated by the sampler differs by 2 percent
or more from the required sampler flow rate, the sampler flow rate
must be adjusted to the required flow rate, under section 7.4.1 of
this appendix.
9.3 Periodic calibration or verification of the calibration of
the sampler's ambient temperature, filter temperature, and
barometric pressure measurement systems is also required. Reference
3 of section 13.0 of this appendix contains additional guidance.

10.0 PM2.5 Measurement Procedure The detailed procedure
for obtaining valid PM2.5 measurements with each specific
sampler designated as part of a reference method for
PM2.5 under part 53 of this chapter shall be provided in
the sampler-specific operation or instruction manual required by
section 7.4.18 of this appendix. Supplemental guidance is provided
in section 2.12 of the Quality Assurance Handbook listed in
reference 2 in section 13.0 of this appendix. The generic procedure
given here serves to illustrate the general steps involved in the
PM2.5 sample collection and measurement, using a
PM2.5 reference method sampler.
10.1 The sampler shall be set up, calibrated, and operated in
accordance with the specific, detailed guidance provided in the
specific sampler's operation or instruction manual and in accordance
with a specific quality assurance program developed and established
by the user, based on applicable supplementary guidance provided in
reference 2 in section 13.0 of this appendix.
10.2 Each new sample filter shall be inspected for correct type
and size and for pinholes, particles, and other imperfections.
Unacceptable filters should be discarded. A unique identification
number shall be assigned to each filter, and an information record
shall be established for each filter. If the filter identification
number is not or cannot be marked directly on the filter,
alternative means, such as a number-identified storage container,
must be established to maintain positive filter identification.
10.3 Each filter shall be conditioned in the conditioning
environment in accordance with the requirements specified in section
8.2 of this appendix.
10.4 Following conditioning, each filter shall be weighed in
accordance with the requirements specified in section 8.0 of this
appendix and the presampling weight recorded with the filter
identification number.
10.5 A numbered and preweighed filter shall be installed in the
sampler following the instructions provided in the sampler operation
or instruction manual.
10.6 The sampler shall be checked and prepared for sample
collection in accordance with instructions provided in the sampler
operation or instruction manual and with the specific quality
assurance program established for the sampler by the user.
10.7 The sampler's timer shall be set to start the sample
collection at the beginning of the desired sample period and stop
the sample collection 24 hours later.
10.8 Information related to the sample collection (site location
or identification number, sample date, filter identification number,
and sampler model and serial number) shall be recorded and, if
appropriate, entered into the sampler.
10.9 The sampler shall be allowed to collect the
PM2.5 sample during the set 24-hour time period.
10.10 Within 96 hours of the end of the sample collection
period, the filter, while still contained in the filter cassette,
shall be carefully removed from the sampler, following the procedure
provided in the sampler operation or instruction manual and the
quality assurance program, and placed in a protective container.
This protective container shall be made of metal and contain no
loose material that could be transferred to the filter. The
protective container shall hold

[[Page 38722]]

the filter cassette securely such that the cover shall not come in
contact with the filter's surfaces. Reference 2 in section 13.0 of
this appendix contains additional information.
10.11 The total sample volume in actual m³ for the
sampling period and the elapsed sample time shall be obtained from
the sampler and recorded in accordance with the instructions
provided in the sampler operation or instruction manual. All sampler
warning flag indications and other information required by the local
quality assurance program shall also be recorded.
10.12 All factors related to the validity or representativeness
of the sample, such as sampler tampering or malfunctions, unusual
meteorological conditions, construction activity, fires or dust
storms, etc. shall be recorded as required by the local quality
assurance program. The occurrence of a flag warning during a sample
period shall not necessarily indicate an invalid sample but rather
shall indicate the need for specific review of the QC data by a
quality assurance officer to determine sample validity.
10.13 After retrieval from the sampler, the exposed filter
containing the PM2.5 sample should be transported to the
filter conditioning environment as soon as possible ideally to
arrive at the conditioning environment within 24 hours for
conditioning and subsequent weighing. During the period between
filter retrieval from the sampler and the start of the conditioning,
the filter shall be maintained as cool as practical and continuously
protected from exposure to temperatures over 25 deg.C. See section
8.3.6 of this appendix regarding time limits for completing the
post-sampling weighing. See reference 2 in section 13.0 of this
appendix for additional guidance on transporting filter samplers to
the conditioning and weighing laboratory.
10.14. The exposed filter containing the PM2.5 sample
shall be re-conditioned in the conditioning environment in
accordance with the requirements specified in section 8.2 of this
appendix.
10.15. The filter shall be reweighed immediately after
conditioning in accordance with the requirements specified in
section 8.0 of this appendix, and the postsampling weight shall be
recorded with the filter identification number.
10.16 The PM2.5 concentration shall be calculated as
specified in section 12.0 of this appendix.
11.0 Sampler Maintenance
The sampler shall be maintained as described by the sampler's
manufacturer in the sampler-specific operation or instruction manual
required under section 7.4.18 of this appendix and in accordance
with the specific quality assurance program developed and
established by the user based on applicable supplementary guidance
provided in reference 2 in section 13.0 of this appendix.
12.0 Calculations
12.1 (a) The PM2.5 concentration is calculated as:
PM2.5 = (Wf - Wi)/Va
where:
PM2.5 = mass concentration of PM2.5,
g/m³;
Wf, Wi = final and initial weights,
respectively, of the filter used to collect the PM2.5
particle sample, g;
Va = total air volume sampled in actual volume units,
as provided by the sampler, m³.
(b) Note: Total sample time must be between 1,380 and 1,500
minutes (23 and 25 hrs) for a fully valid PM2.5 sample;
however, see also section 3.3 of this appendix.
13.0 References.
1. Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume I, Principles. EPA/600/R-94/038a, April 1994.
Available from CERI, ORD Publications, U.S. Environmental Protection
Agency, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268.
2. Copies of section 2.12 of the Quality Assurance Handbook for
Air Pollution Measurement Systems, Volume II, Ambient Air Specific
Methods, EPA/600/R-94/038b, are available from Department E (MD-
77B), U.S. EPA, Research Triangle Park, NC 27711.
3. Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume IV: Meteorological Measurements, (Revised Edition)
EPA/600/R-94/038d, March, 1995. Available from CERI, ORD
Publications, U.S. Environmental Protection Agency, 26 West Martin
Luther King Drive, Cincinnati, Ohio 45268.
4. Military standard specification (mil. spec.) 8625F, Type II,
Class 1 as listed in Department of Defense Index of Specifications
and Standards (DODISS), available from DODSSP-Customer Service,
Standardization Documents Order Desk, 700 Robbins Avenue, Building
4D, Philadelphia, PA 1911-5094.
14.0 Figures L-1 through L-30 to Appendix L.

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Notices For
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994

[[pp. 38702-38752]] National Ambient Air Quality Standards for Particulate Matter

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