40 CFR §1065.265

1. (a)Application. You may use a nonmethane cutter to measure CH4 with a FID analyzer. A nonmethane cutter oxidizes all nonmethane hydrocarbons to CO2 and H2O. You may use a nonmethane cutter for raw or diluted exhaust for batch or continuous sampling.
2. (b)System performance. Determine nonmethane-cutter performance as described in § 1065.365 and use the results to calculate CH4 or NMHC emissions in § 1065.660.
3. (c)Configuration. Configure the nonmethane cutter with a bypass line if it is needed for the verification described in § 1065.365.
4. (d)Optimization. You may optimize a nonmethane cutter to maximize the penetration of CH4 and the oxidation of all other hydrocarbons. You may humidify a sample and you may dilute a sample with purified air or oxygen (O2) upstream of the nonmethane cutter to optimize its performance. You must account for any sample humidification and dilution in emission calculations.