The invention refers to an APU compartment, and a method for extinguishing a fire in an APU compartment. The APU compartment (1) comprises an APU (2), an exhaust (5), an aperture (7) providing a passage between the APU compartment (1) and the inside of the exhaust (5), and a fire detection system, wherein the APU compartment (1) of the invention is constructed as an air tight compartment, and additionally comprises a conduit (9) for providing external air to the APU compartment (1), a door (8) for closing the conduit (9) inlet, and a control unit (6) configured to close the door (8) when a fire is detected, such that when the door (8) is closed and the APU (2) is in operation, the air contained in the APU compartment (1) is sucked through the aperture (7) to be expelled out of the APU compartment (1) to extinguish the fire.