R18-2-202. Sulfur Oxides (Sulfur Dioxide)

A. The primary ambient air quality standards for sulfur oxides, measured as sulfur dioxide, are: 1. 0.03 parts per million (ppm) (80 µg/m3) -- annual arithmetic mean. 2. 0.14 parts per million (ppm) (365 µg/m3) – maximum 24- hour concentration not to be exceeded more than once per calendar year. 3. 75 parts per billion (ppb) – maximum one-hour concentration. The one-hour primary standard is met at an ambient air quality monitoring site when the three-year average of the annual 99th percentile of the daily maximum one-hour average concentrations is less than or equal to 75 parts per billion, as determined according to 40 CFR 50, Appendix T. B. The secondary ambient air quality standard for sulfur oxides, measured as sulfur dioxide, is 0.5 parts per million (ppm) (1300 µg/m3) -- maximum three-hour concentration not to be exceeded more than once per year. C. The level of the standards shall be measured by a reference method based on 40 CFR 50, Appendix A or A-1, or by a Federal Equivalent Method designated according to 40 CFR 53. D. The standards in subsections (A)(1) and (2) shall apply: 1. In an area designated nonattainment for a standard in subsections (A)(1) or (2) as of August 23, 2011, and areas not meeting a state implementation plan call for a standard in subsections (A)(1) or (2), until the state submits pursuant to section 191 of the Act, and the Administrator approves, a state implementation plan providing for attainment the standard in subsection (A)(3) in that area. 2. In areas other than those identified in subsection (D)(1), until the effective date of the designation of that area, pursuant to section 107 of the Act, for the standard in subsection (A)(3).