Applicability. This chapter applies to stationary internal combustion engines used to compress natural gas located at natural gas pipeline compression stations. NOx Emission Limits. A person who owns or operates a stationary internal combustion engine to which this chapter applies shall perform either parametric optimization or engine rebuild to meet the following NOx emission limits: Facilities with five or fewer internal combustion engines shall meet a combined maximum hourly emission limit of 300 pounds per hour or less. Facilities with more than five engines shall meet a combined maximum hourly emission limit of 566 pounds per hour or less. NOx Emission Rates. The NOx emission rates in §C(2) of this regulation apply to a stationary internal combustion engine used to compress natural gas at a natural gas pipeline compression station if the engine is one of the types and corresponding sizes identified in §C(2) of this regulation. Emission Rates. The NOx emission rates in §C(2) of this regulation shall apply on and after May 1, 2003.