PURPOSE: To uniform cleanness in a passenger compartment and prevent energy loss by forming the air conditioner of an aircraft or the like in such a way as to supply each part in the passenger compartment with air of the flow quantity corresponding to the carbon dioxide gas density in each part.

CONSTITUTION: There are provided plural carbon dioxide gas density sensors 3 disposed dispersedly in a passenger compartment, blow-off holes 4 disposed in the vicinity of the installed places of the respective carbon dioxide gas density sensors 3 to blow off air, and plural change-over valves 5 for controlling air supply quantity to the respective blow-off holes 4. Each change-over valve 5 is controlled by the corresponding carbon dioxide gas density sensor 3.