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EPA scientists develop and evaluate Federal Reference & Equivalent Methods for measuring key air pollutants

EPA operates a nationwide air monitoring network to measure six primary air pollutants:  carbon monoxide, lead, sulfur dioxide, ozone, nitrogen dioxide, and particulate matter (PM10 and PM2.5) as part of its mission to protect human health and the environment.

To support monitoring efforts, EPA scientists develop and evaluate methods for accurately and reliably measuring these pollutants in outdoor air. These methods — called Federal Reference Methods (FRMs) — are used by states and other monitoring organizations to assess implementation actions needed to attain the federal Clean Air Act’s National Ambient Air Quality Standards (NAAQS). FRMs are the “gold standard” of air pollution monitoring systems and ensure air quality data collected at different sites are gathered in the same manner and are accurate.

To foster innovation and advance new technologies, EPA also reviews, tests, and approves other methods, called Federal Equivalent Methods (FEMs), which are based on different sampling and/or analyzing technologies than FRMs, but are required to provide the same decision making quality when making NAAQS attainment determinations.

EPA scientists review and establish NAAQS on five-year cycles based on new health and environmental research data. They review and ensure that methods are based on modern technology and have adequate instrument sensitivity to accurately measure pollutants. 

Potential new FRMs are tested for accuracy by EPA scientists in the lab and field. EPA scientists also develop calibration protocols and provide technical assistance to assist states, regions and tribes in using FRMs with their air pollution monitoring systems.

Approved new methods are formally announced through publication in the Federal Register while approved modifications to existing FRMs and/or FEMs are made available several times a year in the list of FRMs/FEMs below. 

Related Links:

Technical Contact:

Robert Vanderpool, Ph.D. (