14 CFR § 25.1181

Designated fire zones are—

The engine power section;

The engine accessory section;

Except for reciprocating engines, any complete powerplant compartment in which no isolation is provided between the engine power section and the engine accessory section;

Any auxiliary power unit compartment;

Any fuel-burning heater and other combustion equipment installation described in § 25.859;

The compressor and accessory sections of turbine engines; and

Combustor, turbine, and tailpipe sections of turbine engine installations that contain lines or components carrying flammable fluids or gases.

Each designated fire zone must meet the requirements of §§ 25.863, 25.865, 25.867, 25.869, and 25.1185 through 25.1203.