40 CFR § 1068.2 - How does this part apply for engines and how does it apply for equipment?
(a) See the standard-setting part to determine if engine-based and/or equipment-based standards apply. (Note: Some equipment is subject to engine-based standards for exhaust emission and equipment-based standards for evaporative emissions.)
(3) Subpart F of this part generally applies to the engines or to the equipment, whichever is subject to standards under the standard-setting part. However, since subpart F of this part addresses in-use engines and equipment (in which the engine is installed in the equipment), the requirements do not always distinguish between engines and equipment.
(c) For issues related to testing, read the term “engines/equipment” to mean engines for engines subject to engine-based testing and equipment for equipment subject to equipment-based testing; otherwise, read the term “ engines/equipment” to mean engines for sources subject to engine-based standards and equipment for sources subject to equipment-based standards.
(d) When we use the term engines (rather than engines/equipment), read it to mean engines without regard to whether the source is subject to engine-based standards or testing. When we use the term equipment (rather than engines/equipment), read it to mean equipment without regard to whether the source is subject to equipment-based standards or testing. (Note: The definition of “equipment” in § 1068.30 includes the engine.)
(e) The terminology convention described in this section is not intended to limit our authority or your obligations under the Clean Air Act.