Equivalent Test Methods/Clean Air Act: U.S. Environmental Protection Agency Designates New Reference Method and Three New Equivalent Methods (PM2.5/PM10-2.5)
August 06, 2026
By:
Walter G. Wright
Category:
Arkansas Environmental, Energy, and Water Law
Arkansas Environmental, Energy, and Water Law
Download PDF
The United States Environmental Protection Agency (“EPA”) published a July 15th Federal Register notice announcing that it has designated the following: One New Reference Method and Three New Equivalent Methods for measuring concentrations of PM2.5. See 91 Fed. Reg. 43372.
EPA describes the methods as follows:
- New reference method for measuring carbon monoxide (CO).
- One new equivalent method for measuring particulate matter (PM) 2.5 micrometers (um) or less (PM2.5).
- One new equivalent method for measuring PM 10 um or less (PM10).
- One new equivalent method for measuring PM10–2.5 in ambient air.
Sampling air conditions is an important part of the process for determining whether an area is and/or will remain in compliance with the Clean Air Act National Ambient Air Quality Standards (“NAAQS”).
Pursuant to the authority of the Clean Air Act and in accordance with regulations 40 C.F.R. Part 53, EPA evaluates methods for monitoring the concentrations of the NAAQS as set for in 40 C.F.R. Part 50. Such monitoring methods must meet certain specific requirements for adequacy as either reference or equivalent for utilizations by states to determine compliance with the applicable NAAQS.
EPA typically announces approval of an equivalent test or monitoring method as it is approved.
A copy of the Federal Register notice can be found here.
The Between the Lines blog is made available by Mitchell, Williams, Selig, Gates & Woodyard, P.L.L.C. and the law firm publisher. The blog site is for educational purposes only, as well as to give general information and a general understanding of the law. This blog is not intended to provide specific legal advice. Use of this blog site does not create an attorney client relationship between you and Mitchell Williams or the blog site publisher. The Between the Lines blog site should not be used as a substitute for legal advice from a licensed professional attorney in your state.