30 C.F.R. § 7.84 – Technical requirements.

(a) Fuel injection adjustment. The fuel injection system of the engine shall be constructed so that the quantity of fuel injected can be controlled at a desired maximum value. This adjustment shall be changeable only after breaking a seal or by altering the design.
(b) Maximum fuel-air ratio. At the maximum fuel-air ratio determined by § 7.87 of this part, the concentrations (by volume, dry basis) of carbon monoxide (CO) and oxides of nitrogen (NOX) in the undiluted exhaust gas shall not exceed the following:
1. (1) There shall be no more than 0.30 percent CO and no more than 0.20 percent NOX for category A engines.
2. (2) There shall be no more than 0.25 percent CO and no more than 0.20 percent NOX for category B engines.
(c) Gaseous emissions ventilation rate. Ventilation rates necessary to dilute gaseous exhaust emissions to the following values shall be determined under § 7.88 of this part:
Carbon dioxide −5000 ppm
Carbon monoxide −50 ppm
Nitric oxide −25 ppm
Nitrogen dioxide −5 ppm
A gaseous ventilation rate shall be determined for each requested speed and horsepower rating as described in § 7.88(b) of this part.
(d) Fuel deration. The fuel rates specified in the fuel deration chart shall be based on the tests conducted under paragraphs (b) and (c) of this section and shall ensure that the maximum fuel:air (f/a) ratio determined under paragraph (b) of this section is not exceeded at the altitudes specified in the fuel deration chart.
(e) Particulate index. For each rated speed and horsepower requested, the particulate index necessary to dilute the exhaust particulate emissions to 1 mg/m ³ shall be determined under § 7.89 of this part.

Carbon dioxide	−5000 ppm
Carbon monoxide	−50 ppm
Nitric oxide	−25 ppm
Nitrogen dioxide	−5 ppm