Ambient Air Monitoring Reference and Equivalent Methods; Designation of One New Reference Method and Three New Equivalent Methods; Correction

Official abstract: On July 15, 2026, the U.S. Environmental Protection Agency (EPA) published a notice designating one new reference method for measuring carbon monoxide (CO), one new equivalent method for measuring particulate matter (PM) 2.5 micrometers (µm) or less (PM<INF>2.5</INF>), one new equivalent method for measuring PM 10µm or less (PM<INF>10</INF>), and one new equivalent method for measuring PM<INF>10-2.5</INF> in ambient air. After publication, the EPA realized that there was an error in the notice; therefore, this action corrects and replaces the July 15, 2026, designation notice.