(a) This part applies to new nonroad spark-ignition engines and vehicles with gross power output at or below 19 kilowatts (kW) used for any purpose, unless we exclude them under paragraph (d) of this section.

(b) In certain cases, the regulations in this part 90 also apply to new engines with a gross power output above 19 kW that would otherwise be covered by 40 CFR part 1048 or 1051. See 40 CFR 1048.615 or 1051.145(a)(3) for provisions related to this allowance.

(c) In certain cases, the regulations in this part 90 apply to new engines below 50 cc used in motorcycles that are motor vehicles. See 40 CFR 86.447-2006 for provisions related to this allowance.

(d) The following nonroad engines and vehicles are not subject to the provisions of this part:

(1) Engines certified to meet the requirements of 40 CFR part 1051 (e.g., engines used in snowmobiles). This part nevertheless applies to engines used in recreational vehicles if the manufacturer uses the provisions of 40 CFR 1051.145(a)(3) to exempt them from the requirements of 40 CFR part 1051. Compliance with the provisions of this part is a required condition of that exemption.

(2) Engines used in highway motorcycles. See 40 CFR part 86, subpart E.

(3) Propulsion marine engines. See 40 CFR part 91. This part applies with respect to auxiliary marine engines.

(4) Engines used in aircraft. See 40 CFR part 87.

(5) Engines certified to meet the requirements of 40 CFR part 1048, subject to the provisions of § 90.913.

(6) Hobby engines.

(7) Engines that are used exclusively in emergency and rescue equipment where no certified engines are available to power the equipment safely and practically, but not including generators, alternators, compressors or pumps used to provide remote power to a rescue tool. The equipment manufacturer bears the responsibility to ascertain on an annual basis and maintain documentation available to the Administrator that no appropriate certified engine is available from any source.

(e) Engines subject to the provisions of this subpart are also subject to the provisions found in subparts B through N of this part, except that Subparts C, H, M and N of this part apply only to Phase 2 engines as defined in this subpart.

(f) Certain text in this part is identified as pertaining to Phase 1 or Phase 2 engines. Such text pertains only to engines of the specified Phase. If no indication of Phase is given, the text pertains to all engines, regardless of Phase.

(g) This part also applies to engines under 50 cc used in motorcycles that are motor vehicles if the manufacturer uses the provisions of 40 CFR 86.447-2006 to meet the emission standards in this part instead of the requirements of 40 CFR part 86. In this case, compliance with the provisions of this part is a required condition of that exemption.