section_subject: "National primary ambient air quality standards for PM"
cfr_reference: "40 CFR 50.18"
title_name: "Title 40"
title_subject: "Protection of Environment"
parts_covered: "Parts 50 to 51"
revised_date: "Revised as of July 1, 2019"
publication_date: "As of July 1, 2019"
contains_description: "Containing a codification of documents of general applicability and future effect"
publication_info: "Published by the Office of the Federal Register National Archives and Records Administration as a Special Edition of the Federal Register"
---
(a)The national primary ambient air quality standards for PM2.5 are 12.0 micrograms per cubic meter (µg/m3) annual arithmetic mean concentration and 35 µg/m3 24-hour average concentration measured in the ambient air as PM2.5 (particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers) by either:
(1)A reference method based on appendix L to this part and designated in accordance with part 53 of this chapter; or
(2)An equivalent method designated in accordance with part 53 of this chapter.
(b)The primary annual PM2.5 standard is met when the annual arithmetic mean concentration, as determined in accordance with appendix N of this part, is less than or equal to 12.0 µg/m3.
(c)The primary 24-hour PM2.5 standard is met when the 98th percentile 24-hour concentration, as determined in accordance with appendix N of this part, is less than or equal to 35 µg/m3.