30 CFR § 57.4262
Underground transformer stations, combustible liquid storage and dispensing areas, pump rooms, compressor rooms, and hoist rooms.
Transformer stations, storage and dispensing areas for combustible liquids,
pump rooms, compressor rooms, and hoist rooms shall be provided with fire
protection of a type, size, and quantity that can extinguish fires of any
class in their early stages which could occur as a result of the hazards