(a) Diesel-powered equipment shall be used underground only with a diesel fuel having a sulfur content no greater than 0.05 percent and a flash point of 100 °F (38 °C) or greater. Upon request, the mine operator shall provide to an authorized representative of the Secretary evidence that the diesel fuel purchased for use in diesel-powered equipment underground meets these requirements.

(b) Flammable liquids shall not be added to diesel fuel used in diesel-powered equipment underground.

(c) Only diesel fuel additives that have been registered by the Environmental Protection Agency may be used in diesel-powered equipment underground.