121.253—Powerplant fire protection.
(a)
Designated fire zones must be protected from fire by compliance with §§ 121.255 through 121.261.
(b)
Designated fire zones are—
(1)
Engine accessory sections;
(2)
Installations where no isolation is provided between the engine and accessory compartment; and
(3)
Areas that contain auxiliary power units, fuel-burning heaters, and other combustion equipment.