(a) What is the purpose of this section? This section limits the amount of sulfur dioxide (SO2) that may be emitted from certain air pollution sources operating within the Indian reservation to control ground-level concentrations of SO2.

(b) Who is affected by this section? This section applies to any person who owns or operates an air pollution source that emits, or could emit, SO2 to the atmosphere.

(c) What is exempted from this section? This section does not apply to furnaces and boilers used exclusively for space heating with a rated heat input capacity of less than 400,000 British thermal units (Btu) per hour, and mobile sources.

(d) What are the sulfur dioxide limits for sources?

(1) Sulfur dioxide emissions from a combustion source stack must not exceed an average of 500 parts per million by volume, on a dry basis and corrected to seven percent oxygen, during any three-hour period.

(2) Sulfur dioxide emissions from a process source stack, or any other stack not subject to (d)(1) of this section, must not exceed an average of 500 parts per million by volume, on a dry basis, during any three-hour period.

(e) What are the reference methods for determining compliance?

(1) The reference methods for determining compliance with the SO2 limits are EPA Methods 6, 6A, 6B, and 6C as specified in the applicability section of each method. A complete description of these methods is found in appendix A of 40 CFR part 60.

(2) An alternative reference method is a continuous emissions monitoring system (CEMS) that complies with Performance Specification 2 found in appendix B of 40 CFR part 60.

(f) Definitions of terms used in this section. The following terms that are used in this section are defined in §49.123 General provisions: Act, air pollutant, air pollution source, ambient air, British thermal unit (Btu), coal, combustion source, continuous emissions monitoring system (CEMS), distillate fuel oil, emission, fuel, fuel oil, gaseous fuel, heat input, incinerator, marine vessel, mobile sources, motor vehicle, nonroad engine, nonroad vehicle, open burning, process source, reference method, refuse, residual fuel oil, solid fuel, stack, standard conditions, stationary source, used oil, wood, and woodwaste burner.