9VAC5-30-68. Particulate matter (PM2.5)

A. The national primary ambient air quality standards for PM 2.5 are 9.0 micrograms per cubic meter (µg/m 3 ) annual arithmetic mean concentration and 35 µg/m 3 24-hour average concentration measured in the ambient air as PM 2.5 (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 40 CFR Part 50 and designated in accordance with 40 CFR Part 53; or 2. An equivalent method designated in accordance with 40 CFR Part 53. B. The primary annual PM 2.5 standard is met when the annual arithmetic mean concentration, as determined in accordance with Appendix N to 40 CFR Part 50, is less than or equal to 9.0 µg/m 3 . C. The primary 24-hour PM 2.5 standard is met when the 98th percentile 24-hour concentration, as determined in accordance with Appendix N to 40 CFR Part 50, is less than or equal to 35 µg/m 3 .