Rule 17.8.210 - AMBIENT AIR QUALITY STANDARDS FOR SULFUR DIOXIDE(1) No person shall cause or contribute to concentrations of sulfur dioxide in the ambient air which exceed any of the following standards: (a) hourly average: 0.50 ppm, one-hour average, not to be exceeded more than 18 times in any 12 consecutive months;(b) twenty-four hour average: 0.10 ppm, 24-hour average, not to be exceeded more than once per year;(c) annual average: 0.02 ppm, annual average, not to be exceeded.(2) For determining compliance with this rule, sulfur dioxide shall be measured by the pararosaniline method as more fully described in 40 CFR Part 50, Appendix A, incorporated by reference in ARM 17.8.202, or by an approved equivalent method.NEW, 1980 MAR p. 2399, Eff. 8/15/80; AMD, 1987 MAR p. 1482, Eff. 8/28/87; AMD, 1996 MAR p. 1844, Eff. 7/4/96; TRANS, from DHES, 1996 MAR p. 2285; AMD, 1997 MAR p. 1582, Eff. 9/9/97.75-2-111, 75-2-202, MCA; IMP, 75-2-202, MCA;