AIR CONDITIONER

PURPOSE:To prevent an air conditioned state of an air conditioned room from being deteriorated by a method wherein an amount of surrounding air is adjusted in its volumetric manner in such a way as it may become a predetermined amount corresponding to an amount of fed air calculated in response to a detected temperature information of the temperature sensing means for sensing a temperature of the air conditioned room. CONSTITUTION:A heat exchanger 5 and an air feeding fan 6 connected to an external heat source device 3 are arranged in an air passage forming part 2 of an air conditioner. Returned air RA from an air conditioned room is fed from a circulation air duct 7, heat exchanged with a heat exchanger 5 and further fed to the air conditioned room R through the air feeding duct 8 as supply air SA. A part of the circulated air RA is discharged through a discharging duct 11 and the surrounding air OA is sucked through the surrounding air duct 9 to perform a ventilation of it. When this ventilation is carried out, an amount of air passing through each of the ducts 9 and 11 is detected by air volume sensing means 16 and 17 and the amount of surrounding air OA is adjusted in such a way as it becomes the predetermined amount of air corresponding to the air volume of the fed air SA and thus each of the air volume adjusting means 12 and 13 is controlled.