Natural gas

Natural gas means a naturally occurring mixture or process derivative of hydrocarbon and non-hydrocarbon gases found in geologic formations beneath the earth's surface, of which its constituents include, but are not limited to, methane, heavier hydrocarbons and carbon dioxide. Natural gas may be field quality, pipeline quality, or process gas.

Source

40 CFR § 98.238

Scoping language

Except as provided in this section, all terms used in this subpart have the same meaning given in the Clean Air Act and subpart A of this part.