New and Revised Frequent Questions About
The following part 75 monitoring Q&As are either new or revised and have not yet been added to the Part 75 Emissions Monitoring Policy Manual PDF document.
- Question 6.6 (added on 4/14/2022)
- Question 7.14 (added on 9/28/2020)
- Question 8.15 (revised on 9/25/2019)
- Question 9.34 (revised on 9/20/2022)
- Question 13.18 (revised on 4/4/2019)
- Question 23.21 (added on 9/28/2020)
- Question 23.22 (added on 9/28/2020)
- Question 23.23 (added on 9/28/2020)
- Question 27.22 (added on 9/28/2020)
Section 6: CO2 Monitoring - Question 6.6
Topic: CO2 Mass Calculated According to Appendix G Equation G-4
Question: Regarding the calculation of hourly CO2 mass (tons/hr) using equation G-4 found in appendix G to part 75, may I calculate a site-specific FC-factor in accordance with the procedures found in section 3.3.6 of appendix F to part 75? May I also pro-rate the FC-factor in accordance with the procedures found in section 3.3.6.4 of appendix F to part 75 if multiple oil or gaseous fuels (as defined in 40 CFR §72.2) are fired in a clock hour?
Answer: Yes, reporters using equation G-4 to calculate hourly CO2 mass (tons/hr) may either use the table default FC-factor found in section 3.3.5 of appendix F to part 75, for fuels found in Table 1 of appendix F, or calculate a site-specific FC-factor in accordance with the procedures found in section 3.3.6 of appendix F to part 75 for oil or gaseous fuels (as defined in 40 CFR §72.2). During clock hours when multiple oil or gaseous fuels (as defined in 40 CFR §72.2) are fired in a clock hour, the pro-rating procedures found in section 3.3.6.4 of appendix F to part 75 should be used to calculate the FC-factor found in equation G-4. Note that the use of equation G-4 is limited to only oil or gas-fired (as defined in 40 CFR §72.2) units which primarily rely on appendix D to part 75 to determine hourly heat input.
References: § 3.3.5, § 3.3.6, and § 3.3.6.4 of appendix F to part 75 and § 2.3 of appendix G to part 75
History: Added on April 14, 2022
Section 7: Backup and Portable Monitoring - Question 7.14
Topic: Testing requirements for like-kind analyzers used more than 720 hours
Question: What tests are required to use a like-kind analyzer for more than 720 hours per calendar year?
Answer: If a like-kind analyzer is used for more than 720 hours per calendar year at a monitoring location, you must update the monitoring plan to add the analyzer as a component of a regular non-redundant backup system. In addition, the monitoring system, including the like-kind analyzer must pass a relative accuracy test audit (RATA) at that monitoring location prior to reporting data greater than 720 hours per calendar year at a monitoring location or you must report the data as invalid.
In the case where a like-kind analyzer replaces one component of a NOx-diluent monitoring system, a RATA is required on the complete NOx-diluent monitoring system, not just the like-kind analyzer component. For example, if you replace a CO2 analyzer in a NOx-diluent monitoring system with a like-kind analyzer and the NOx concentration monitor continues to function normally, you must still conduct a relative accuracy test audit (RATA) on the NOx-diluent monitoring system in lb/mmBtu.
If a like-kind analyzer is used for more than 720 hours in a calendar year, but not more than 720 hours at a single monitoring location during the calendar year (i.e., the like-kind analyzer was used at two or more monitoring locations for less than 720 hours in each location), a RATA is not required.
References: § 75.20(d)(2)(v)
History: Added on September 28, 2020
Section 8: Relative Accuracy - Question 8.15
Topic: RATA load requirements for common stacks
Question: Our company has a plant with three units using a common stack. One of those units experienced an unscheduled outage during the last quarter in which we should perform an annual flow RATA at three load levels. Should we wait to perform the RATA for flow until all three units are operating again?
Answer: Every effort should be made to perform the relative accuracy test audit by the end of the required quarter. Section 6.5.2.1 of appendix A defines the range of operation for a unit or common stack. For common stacks, the range of operation extends from the minimum safe, stable load of any unit using the stack to the highest sustainable load with all units in operation. Section 6.5.2.1 further defines the low, mid, and high load levels as 0–30%, 30–60%, and 60–100% of the range of operation, respectively.
Therefore, in the present example, if a load level of at least 60% of the range of operation could be attained with two units in operation, this would suffice for the high-level flow RATA. The mid- and low-flow tests could then be done at 35% and 10% of the operating range, respectively (note that section 6.5.2 of appendix A requires a minimum separation of 25% of the operating range between adjacent load levels).
If, however, a true high level data point is not attainable with only two units in operation, then if it is expected that all three units will be back in service soon after the end of the quarter, perform the high-level flow RATA within the 720 unit operating hour grace period allowed under section 2.3.3 of appendix B. If it is expected that all three units will not be back in service within the 720 unit-operating-hour grace period, contact your EPA monitoring analyst.
References: appendix A, sections 6.5.2 and 6.5.2.1; appendix B, sections 2.3.1 and 2.3.3
History: First published in March 1995, Update #5; revised in October 1999 Revised Manual; revised in 2013 Manual, Revised 9/25/2019]
Section 9: Span, Calibration, and Linearity - Question 9.34
Topic: Use of EPA Protocol Gas Components for Calibration
Question: Should the NO or the NOX concentration on an EPA Protocol gas cylinder be used for NOX analyzer calibrations and linearity checks?
Answer: Prior to 2004, only the NO component of EPA Protocol gas cylinders was certified as traceable to the National Institute of Standards and Technology (NIST); the NOX concentrations shown on calibration gas certificates were for informational use only. However, since then, NIST may have certified both the NO and NOX concentrations of Standard Reference Materials (SRMs) and NIST Traceable Reference Materials (NTRMs). Therefore, it is possible for specialty gas companies to produce EPA Protocol gas cylinders in which both the NO and NOX concentrations are NIST traceable.
In view of this:
1. When both the NO and NOX concentrations of an EPA Protocol gas cylinder are certified NIST-traceable:
- If the analyzer measures total NOX, you may use either the certified NO concentration or the certified NOX concentration when conducting calibration error tests or linearity checks. However, you must compare the same gas constituents, that is, you must compare the certified NO concentration to the analyzer NO concentration response or the certified NOX concentration to the analyzer NOX concentration response. Therefore, for NOX analyzers that measure total NOX, if NOX is the target value then the NOX analyzer needs to operate in the NOX measurement mode and if NO is the target value then the NOX analyzer needs to operate in the NO measurement mode, or
- If the analyzer measures only NO, rather than total NOX, use the certified NO concentration for calibration error tests and linearity checks.
2. If only the NO concentration of the EPA Protocol gas cylinder is NIST-traceable and the NOX concentration is not, use the certified NO concentration for calibration error tests and linearity checks and compare that to the NO concentration response of the analyzer.
References: Appendix A, § 6.2 and 6.3; Appendix B § 2.1.1 and 2.2.1
Key Words: EPA Protocol gas, calibration gas, calibration error test, linearity check, NOX monitoring
History: First published in the 2013 Manual. Updated on 09/20/2022.
Section 13: DAHS, Recordkeeping, and Reporting - Question 13.18
Topic: Minimum data acquisition and handling system requirements for units reporting using the low-mass emitter (LME) methodology
Question: What are the minimum requirements for a data acquisition and handling system (DAHS) for low-mass emitter (LME) units?
Answer: For LME units, a DAHS is not required. Quality assurance test information, monitoring plans, fuel sampling results, and quarterly emissions data for LME units may be generated using the LME module of the ECMPS client tool or imported into ECMPS in XML format.
References: appendix A, section 4
History: First published in November 1995, Update #7; revised in 2013 Manual, revised on 4/24/2019 to reflect DAHS requirements for LME
Section 23: Appendix D - Question 23.21
Topic: Establishment of the fuel flow-to-load ratio test baseline
Question: May I use an initial fuel flow meter certification per appendix D, section 2.1.7.1(a) to establish the beginning of a baseline fuel flow-to-load ratio?
Answer: Yes, baseline data collection may begin with the first hour of fuel flowmeter operation following completion of the most recent quality assurance procedure, including initial fuel flow meter certification.
References: appendix D, sections 2.1.7
History: Added on September 28, 2020
Section 23: Appendix D - Question 23.22
Topic: Fuel flowmeter minimum data capture requirements
Question: What are the hourly minimum data capture requirements for fuel flowmeters?
Answer: Each fuel flowmeter must meet the minimum data capture requirement for continuous monitoring systems in § 75.10(d)(1)—a minimum of one valid data point (e.g., one-minute average) must be obtained in each 15-minute quadrant of each unit operating hour, except when required quality assurance activities are conducted during the hour, in which case, only two valid data points, separated by at least 15-minutes, are required.
References: § 75.10(d)(1)
History: Added on September 28, 2020
Section 23: Appendix D - Question 23.23
Topic: Multi-hole orifice plates
Question: For multi-hole orifice plates, can I use American Gas Association (AGA) Report No. 3 or ASME MFC-3M as an acceptable method for meeting the initial fuel flow meter certification requirements found in section 2.1.5 of appendix D or the ongoing fuel flow meter quality assurance requirements found in section 2.1.6 of appendix D?
Answer: No, the design specifications in AGA Report No. 3 and ASME MFC-3M that are used to meet the requirements of part 75 are for single-hole orifice plates, defined in the reports as a single circular concentric aperture. A multi-hole orifice plate does not meet the initial certification requirements of section 2.1.5 of appendix D by design. However, a multi-hole orifice plate can meet the initial certification and ongoing quality assurance requirements of sections 2.1.5 and 2.1.6, respectively, by conforming with the testing requirements detailed in section 2.1.5.2 of appendix D.
References: appendix D, sections 2.1.5 and 2.1.6
History: Added on September 28, 2020
Section 27: Low Mass Emitters - Question 27.22
Topic: Startups, shutdowns, and partially controlled hours in the low-mass emitter (LME) methodology
Question: For units with add-on NOx controls, dry low-NOx burners, or steam or water injection, what should be reported for hours when the monitored parameters are not within the acceptable envelopes for either the full hour or partial hour?
Answer: If the monitored parameters that indicate proper operation of the NOx emission controls are not within the acceptable ranges for the entire hour, then you must report the appropriate default NOx emission rate from Table LM-2 for the entire hour.
References: § 75.19(c)(1)(iv)(H)
History: Added on September 28, 2020