Section 243.122  Sulfur Oxides (Sulfur Dioxide)

a)         Primary Standards.  The primary ambient air quality standards for sulfur oxides measured as sulfur dioxide are:

1)         An annual arithmetic mean concentration of 80 µg/m³ (0.03 ppm); and

2)         A maximum 24-hour concentration, not to be exceeded more than once per year, of 365 µg/m³ (0.14 ppm).

b)         Secondary Standard.  The secondary ambient air quality standard for sulfur oxides measured as sulfur dioxide is a maximum 3-hour concentration not to be exceeded more than once per year of 1,300 µg/m³ (0.5 ppm).

c)         Measurement Method.  For determining conformance with sulfur oxide air quality standards, sulfur oxides shall be measured as sulfur dioxide by the pararosaniline method described in 40 CFR 50, appendix A (incorporated by reference in Section 243.108), or by an equivalent method of proof approved by the Agency.

(Source:  Amended at 35 Ill. Reg. 18857, effective October 25, 2011)