9VAC5-30-60. Particulate matter (PM<asb>10</asb>)

A. 1. The primary and secondary 24-hour ambient air quality standard is 150 micrograms per cubic meter--24-hour average concentration. 2. The standard is attained when the expected number of days per calendar year with a 24-hour average concentration above 150 micrograms per cubic meter, as determined in accordance with Appendix K of 40 CFR Part 50, is equal to or less than one. B. (Reserved.) C. For the purpose of determining attainment of the primary and secondary standards, particulate matter shall be measured in the ambient air as PM 10 (particles with an aerodynamic diameter less than or equal to a nominal 10 micrometers) by a reference method based on Appendix J of 40 CFR Part 50, or other method designated as such, or by an equivalent method.