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

Document Headings Document headings vary by document type but may contain the following: the agency or agencies that issued and signed a document the number of the CFR title and the number of each part the document amends, proposes to amend, or is directly related to the agency docket number / agency internal file number the RIN which identifies each regulatory action listed in the Unified Agenda of Federal Regulatory and Deregulatory Actions See the Document Drafting Handbook for more details. Environmental Protection Agency [FRL-13145-02-OAR] AGENCY: Environmental Protection Agency (EPA). ACTION: Notice. SUMMARY: 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 2.5 ), one new equivalent method for measuring PM 10µm or less (PM 10 ), and one new equivalent method for measuring PM 10-2.5 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. FOR FURTHER INFORMATION CONTACT: For further information about this notice, contact Reference and Equivalency Methods Program, Air Quality Assessment Division, Office of State Air Partnerships, U.S. Environmental Protection Agency, P.O. Box 12055, 109 T.W. Alexander Drive, Research Triangle Park, North Carolina 27711, email address: FRMFEM@epa.gov . SUPPLEMENTARY INFORMATION: On July 15, 2026 ( 91 FR 43372 ), 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 2.5 ), one new equivalent method for measuring PM 10µm or less (PM 10 ), and one new equivalent method for measuring PM 10-2.5 in ambient air. After…