40 CFR § 1036.101 - Overview of exhaust emission standards.
(a) You must show that engines meet the following exhaust emission standards:
(1) Criteria pollutant standards for NOX, HC, PM, and CO apply as described in § 1036.104. These pollutants are sometimes described collectively as “criteria pollutants” because they are either criteria pollutants under the Clean Air Act or precursors to the criteria pollutants ozone and PM.
(2) This part contains standards and other regulations applicable to the emission of the air pollutant defined as the aggregate group of six greenhouse gases: carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. Greenhouse gas (GHG) standards for CO2, CH4, and N2O apply as described in § 1036.108.
(b) You may optionally demonstrate compliance with the emission standards of this part by testing hybrid powertrains, rather than testing the engine alone. Except as specified, provisions of this part that reference engines apply equally to hybrid powertrains.