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 ([micro]m) or less (PM<INF>2.5</INF>), one new equivalent method for measuring PM 10[micro]m 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.
Source
https://www.federalregister.gov/documents/2026/07/20/2026-14545/ambient-air-monitoring-reference-and-equivalent-methods-designation-of-one-new-reference-method-andCanonical document at the regulator. Always cite this URL — not the Vantage detail page — in compliance evidence.