Measurement method · US EPA
US EPA Federal Reference / Equivalent Method (FRM/FEM)
Federal Reference Methods (FRM) and Federal Equivalent Methods (FEM) are the measurement methods the US Environmental Protection Agency (EPA) formally designates for monitoring the criteria air pollutants that the National Ambient Air Quality Standards (NAAQS) regulate. An FRM is the definitive procedure (a specified instrument and protocol) against which a pollutant is measured, such as the gravimetric filter method for particulate matter or the reference analyzer method for ozone. An FEM is an alternative method that the EPA has tested and found to produce results equivalent to the reference method. It allows continuous or more convenient monitoring in place of the reference procedure.
The standard
What the EPA FRM and FEM Designations Are
Only data from FRM or FEM instruments, operated under strict quality assurance, can be used to judge compliance with the NAAQS. The designations are therefore the gatekeeper of regulatory air-quality data in the United States.
Who uses it
Who Uses It
State, local, and tribal air agencies operate FRM and FEM instruments in the regulatory monitoring networks that determine whether a region attains the NAAQS. Instrument manufacturers seek FRM or FEM designation for their analyzers so that agencies can buy them for compliance use, and industrial operators, consultants, and researchers use designated methods where their data must carry regulatory weight. Anyone whose air-quality measurements might feed a compliance or permitting decision has reason to use, or benchmark against, an FRM or FEM.
Monitoring
How It Relates to Monitoring
The FRM/FEM framework is what separates data that can determine NAAQS attainment from data that merely informs. A designated instrument, sited and operated to the EPA's quality-assurance requirements, produces the measurements compared against the NAAQS. Because each designation covers a single pollutant and method, a full regulatory station combines several designated instruments (a particulate monitor, an ozone analyzer, and gas analyzers for the other criteria pollutants) together with meteorology. Lower-cost sensors are increasingly deployed around these reference stations for spatial coverage. They are corrected against the FRM/FEM data and supplement it rather than replace it, so the designated methods remain the anchor of the network.
Devices
Instruments Built to EPA FRM/FEM
Instruments in the sensor catalog that follow this method. Each connects to Environet through a Thiamis gateway.
Instruments built to it
Solutions
Solutions That Rely on EPA FRM/FEM
Outdoor Monitoring
Continuous outdoor air quality networks that sit alongside reference monitors
Article Library
Articles on EPA FRM/FEM
Ambient Air Quality Monitoring: What Nonattainment Changes
Ambient air quality monitoring explained: how PM2.5 attainment is measured, what a nonattainment designation triggers, and what site-level monitoring adds.
Ozone Exposure Limits and Monitoring: OSHA and NAAQS
OSHA's ozone PEL is 0.1 ppm as an 8-hour TWA. How NIOSH, ACGIH, and the 70 ppb NAAQS compare, and why ozone needs short-interval monitoring.
Questions
EPA FRM/FEM FAQ
What is the difference between an FRM and an FEM?
A Federal Reference Method is the definitive, specified procedure for measuring a criteria pollutant, while a Federal Equivalent Method is an alternative the EPA has demonstrated gives equivalent results. FEMs often allow continuous automated measurement where the reference method is a manual or laboratory procedure. That gives agencies more practical instruments for the same regulatory purpose.
Why can't any sensor be used for NAAQS compliance?
Compliance decisions carry legal and economic consequences, so the data must be comparable across the country and defensible over time. Only FRM and FEM instruments, run under the EPA's quality-assurance rules, provide that consistency. Other sensors may be accurate but are not designated for regulatory decisions.
Do FRM and FEM instruments cover every pollutant at once?
No. Each designation applies to a single pollutant and method, so a station must combine several designated instruments to cover the criteria pollutants, for example a particulate monitor plus separate ozone and gas analyzers. Meteorological sensors are added to interpret the results.
How do I build a regulatory-grade monitoring station?
Combine the FRM or FEM instruments for the pollutants you must report (a particulate monitor, an ozone analyzer, and gas analyzers) with wind and weather sensors, all operated to the required quality-assurance procedures. Use the configurator to assemble the station and add supplementary sensors for spatial coverage.
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