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EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards (174 pp, 1.62 MB) (May 2012)

Use of this protocol is mandatory for certifying the calibration gases being used for the calibration and audit of ambient air quality analyzers and continuous emission monitors that are required by 40 CFR Parts 50, 58, 60, and 75. This protocol describes three procedures for assaying candidate standards (i.e., not-yet-certified standards) and for certifying that their concentrations are traceable to a National Institute of Standards and Technology (NIST) compressed gas reference standards [i.e., Standard Reference Materials (SRMs), NIST-Traceable Reference Materials [NTRMs, including NTRM-Primes (NTRM*s) for which NIST analyzes every sample in the production lot], and NIST Research Gas Materials (RGMs)]. It may be used to assay and certify only candidate standards that have the same components and concentration ranges as NIST-traceable reference standards. A multiple-component candidate standard may be assayed and certified under this protocol if NIST-traceable reference standards that contain the same individual components as are in the candidate standard exist.

This protocol may be used by specialty gas producers, end users, or other laboratories to assay candidate standards. The assay involves the direct comparison of the candidate standards to NIST-traceable reference standards without dilution (i.e., Procedure G1) or the indirect comparison of the candidate standards to reference standards with dilution (i.e., Procedure G2). A candidate standard having a concentration that is lower or higher than that of the reference standard may be certified under this protocol if both standards' concentrations (or diluted concentrations) fall within the well-characterized region of the analyzer's calibration curve. This protocol places no restrictions on cylinder sizes and the same analytical procedures must be used in assays of all cylinder sizes.

Standards that are certified under this protocol must remain in the cylinders in which they were originally assayed. Unassayed standards in cylinders that have been transfilled from cylinders assayed under this protocol cannot be certified as being EPA Protocol Gases.

This protocol may be used to assay and certify zero air materials. Certified impurity concentrations can be certified using Procedures G1 or G2. Procedure G3 can be used to certify that zero air materials conform to the purity specifications of 40 CFR Part 72.2 (i.e., concentrations of SO2, NOX, and THC are not greater than 0.1 ppm; whose concentration of CO is not greater than 1 ppm; and whose concentration of CO2 is not greater than 400 ppm).

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