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2010 EPA Protocol Gas Audit Background

Emissions Monitoring

In 2010, EPA, in cooperation with the National Institute of Standards and Technology (NIST), conducted a blind audit of EPA Protocol gases that are used to calibrate continuous emission monitoring systems (CEMS) and the instruments used in EPA reference methods ( audit summary table and full audit report ). These gases and the associated quality assurance/quality control (QA/QC) checks help ensure the quality of the emission data that EPA uses to assess achievement of emission reductions required under the Clean Air Act. The audit has four main objectives: (1) to ensure that EPA Protocol gases meet the accuracy requirements of 40 CFR Part 75; (2) to provide an incentive for gas vendors that performed well in the audit to continue to use good practices; (3) to encourage gas vendors that performed poorly in the audit to make improvements; and (4) to assist calibration gas consumers in their purchasing decisions.

The results of the 2010 audit are generally consistent with previous audits. The 2010 audit of EPA Protocol gases found a 10% failure rate over all components analyzed, with 40% of the production sites failing at least one gaseous component.

EPA mailed to each vendor a redacted version of the draft audit report containing only that vendor's discrete results and documentation of the NIST cylinder analysis. Some vendors submitted comments on the draft audit report. All vendors that failed one or more components provided statements to EPA and NIST describing corrective actions they took to fix problems and chose to re-analyze their failed cylinders. The vendors then assigned a new concentration value (i.e., tag value) to those cylinders that met the plus or minus 2.0% accuracy requirement in Part 75. EPA and NIST incorporated the comments received from vendors and their re-analyzed concentrations in the audit report.

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