40 CFR § 1048.620 - What are the provisions for exempting large engines fueled by natural gas or liquefied petroleum gas?
(a) If an engine meets all the following criteria, it is exempt from the requirements of this part:
(1) The engine must operate solely on natural gas or liquefied petroleum gas.
(2) The engine must have maximum engine power at or above 250 kW.
(3) The engine must be in an engine family that has a valid certificate of conformity showing that it meets emission standards for engines of that power rating under 40 CFR part 1039.
(b) The only requirements or prohibitions from this part that apply to an engine that is exempt under this section are in this section.
(c) If your engines do not meet the criteria listed in paragraph (a) of this section, they will be subject to the provisions of this part. Introducing these engines into commerce without a valid exemption or certificate of conformity violates the prohibitions in 40 CFR 1068.101.
(d) Engines exempted under this section are subject to all the requirements affecting engines under 40 CFR part 1039. The requirements and restrictions of 40 CFR part 1039 apply to anyone manufacturing engines exempted under this section, anyone manufacturing equipment that uses these engines, and all other persons in the same manner as if these were nonroad diesel engines.
(e) You may request an exemption under this section by submitting an application for certification for the engines under 40 CFR part 1039.