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Air and Climate Change Research

EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards

EPA's air monitoring regulations require the use of Protocol Gases to set air pollution monitors. This protocol helps to ensure that air pollution measurements are accurate and can be trusted. It provides specialty gas producers with a recipe to make calibration gases. In past years, EPA findings showed that commercial calibration gases were too inaccurate and too unstable to use. The protocol was developed jointly by EPA, National Institute of Standards and Technology (NIST), the auto industry, and specialty gas producers.  The procedure balances the government's need for accuracy with the producers' need for flexibility, low cost, and minimum external oversight. EPA verifies the quality of these gases by conducting blind tests of samples purchased from the producers' routine production.

Technical corrections are being made to the EPA Traceability Protocol. When completed, they will be posted on this page. In the interim, draft versions of the corrected content are available from the contact that is listed below.

EPA Protocol Gases at a Glance

  • Compressed gases used to calibrate air pollution monitors for consistent and reliable monitoring
  • Certified concentrations are traceable to gaseous NIST reference standards
  • Prepared, analyzed, and certified by specialty gas producers using EPA traceability protocol
  • EPA Acid Rain Regulations require +/- 2% accuracy

Protocol Gas Verification Programs


Robert S. Wright

Air and Climate Change Research | Water Research | Ecosystems Restoration Research | Land Research | Technology: Sustainable Technologies Research, Environmental Technology Verification Program (ETV), and Technology Assessments

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