Regulations last checked for updates: Feb 03, 2026

Title 40 - Protection of Environment last revised: Dec 31, 2026
All TitlesTitle 40Chapter IPart 60Subpart KKKKaAppendix - Table 1 to Subpart KKKKa of Part 60—Nitrogen Oxide Emission Standards for Stationary Combustion Turbines
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Appendix - Table 1 to Subpart KKKKa of Part 60—Nitrogen Oxide Emission Standards for Stationary Combustion Turbines
Combustion turbine type Combustion turbine base load rated heat input
(HHV) 		Input-based NOX
emission standard 1 		Optional output-based NOX standard 2
New, firing natural gas with utilization rate >45 percent>850 MMBtu/h5 ppm at 15 percent O2 or 7.9 ng/J (0.018 lb/MMBtu)0.054 kg/MWh-gross (0.12 lb/MWh-gross) 0.055 kg/MWh-net (0.12 lb/MWh-net).
New, firing natural gas with utilization rate ≤45 percent and with design efficiency ≥38 percent>850 MMBtu/h25 ppm at 15 percent O2 or 40 ng/J (0.092 lb/MMBtu)0.38 kg/MWh-gross (0.83 lb/MWh-gross) 0.39 kg/MWh-net (0.85 lb/MWh-net).
New, firing natural gas with utilization rate ≤45 percent and with design efficiency <38 percent>850 MMBtu/h9 ppm at 15 percent O2 or 14 ng/J (0.033 lb/MMBtu)0.17 kg/MWh-gross (0.37 lb/MWh-gross) 0.17 kg/MWh-net (0.38 lb/MWh-net).
New, modified, or reconstructed, firing non-natural gas>850 MMBtu/h42 ppm at 15 percent O2 or 70 ng/J (0.16 lb/MMBtu)0.45 kg/MWh-gross (1.0 lb/MWh-gross) 0.46 kg/MWh-net (1.0 lb/MWh-net).
Modified or reconstructed, firing natural gas, at all utilization rates, with design efficiency ≥38 percent>850 MMBtu/h25 ppm at 15 percent O2 or 40 ng/J (0.092 lb/MMBtu)0.38 kg/MWh-gross (0.83 lb/MWh-gross) 0.39 kg/MWh-net (0.85 lb/MWh-net).
Modified or reconstructed, firing natural gas, at all utilization rates, with design efficiency <38 percent>850 MMBtu/h15 ppm at 15 percent O2 or 24 ng/J (0.055 lb/MMBtu)0.28 kg/MWh-gross (0.62 lb/MWh-gross) 0.29 kg/MWh-net (0.30 lb/MWh-net).
New, firing natural gas, at utilization rate >45 percent>50 MMBtu/h and ≤850 MMBtu/h15 ppm at 15 percent O2 or 24 ng/J (0.055 lb/MMBtu)0.20 kg/MWh-gross (0.43 lb/MWh-gross) 0.20 kg/MWh-net (0.44 lb/MWh-net).
New, firing natural gas, at utilization rate ≤45 percent>50 MMBtu/h and ≤850 MMBtu/h25 ppm at 15 percent O2 or 40 ng/J (0.092 lb/MMBtu)0.54 kg/MWh-gross (1.2 lb/MWh-gross) 0.56 kg/MWh-net (1.2 lb/MWh-net).
Modified or reconstructed, firing natural gas>20 MMBtu/h and ≤850 MMBtu/h42 ppm at 15 percent O2 or 67 ng/J (0.15 lb/MMBtu)0.91 kg/MWh-gross (2.0 lb/MWh-gross) 0.92 kg/MWh-net (2.0 lb/MWh-net).
New, firing non-natural gas>50 MMBtu/h and ≤850 MMBtu/h74 ppm at 15 percent O2 or 120 ng/J (0.29 lb/MMBtu)1.6 kg/MWh-gross (3.6 lb/MWh-gross) 1.6 kg/MWh-net (3.7 lb/MWh-net).
Modified or reconstructed, firing non-natural gas>20 MMBtu/h and ≤850 MMBtu/h96 ppm at 15 percent O2 or 160 ng/J (0.37 lb/MMBtu)2.1 kg/MWh-gross (4.7 lb/MWh-gross) 2.2 kg/MWh-net (4.8 lb/MWh-net).
New, firing natural gas≤50 MMBtu/h25 ppm at 15 percent O2 or 40 ng/J (0.092 lb/MMBtu)0.64 kg/MWh-gross (1.4 lb/MWh-gross) 0.65 kg/MWh-net (1.4 lb/MWh-net).
New, firing non-natural gas≤50 MMBtu/h96 ppm at 15 percent O2 or 160 ng/J (0.37 lb/MMBtu)2.4 kg/MWh-gross (5.3 lb/MWh-gross) 2.5 kg/MWh-net (5.4 lb/MWh-net).
Modified or reconstructed, all fuels≤20 MMBtu/h150 ppm at 15 percent O2 or 240 ng/J (0.55 lb/MMBtu)3.9 kg/MWh-gross (8.7 lb/MWh-gross) 4.0 kg/MWh-net (8.9 lb/MWh-net).
New, firing natural gas, either offshore turbines, turbines bypassing the heat recovery unit, and/or temporary turbines>50 MMBtu/h25 ppm at 15 percent O2 or 40 ng/J (0.092 lb/MMBtu)N/A.
Located north of the Arctic Circle (latitude 66.5 degrees north), operating at ambient temperatures less than 0 °F (−18 °C), modified or reconstructed offshore turbines, operated during periods of turbine tuning, byproduct-fired turbines, and/or operating at less than 70 percent of the base load rating≤300 MMBtu/h150 ppm at 15 percent O2 or 240 ng/J) 0.55 lb/MMBtuN/A.
Located north of the Arctic Circle (latitude 66.5 degrees north), operating at ambient temperatures less than 0 °F (−18 °C), modified or reconstructed offshore turbines, operated during periods of turbine tuning, byproduct-fired turbines, and/or operating at less than 70 percent of the base load rating>300 MMBtu/h96 ppm at 15 percent O2 or 150 ng/J (0.35 lb/MMBtu)N/A.
Heat recovery units operating independent of the combustion turbineAll sizes54 ppm at 15 percent O2 or 86 ng/J) 0.20 lb/MMBtuN/A.

1 Input-based standards are determined on a 4-operating-hour rolling average basis.

2 Output-based standards are determined on a 30-operating-day average basis.

authority: 42 U.S.C. 7401
source: 36 FR 24877, Dec. 23, 1971, unless otherwise noted.
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