Section 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.