PURPOSE: To make it possible to reduce the size of a device by furnishing heat reservoirs attached to a burner with a switching function between combustion air blowing and exhaust gas suction.

CONSTITUTION: Heat reservoirs 10a and 10b are housed in bodies 14a and 14b respectively while the bodies 14a and 14b are connected with a combustion air pipeline 15 and an exhaust gas suction pipeline 16 respectively. The heat reservoirs 10a and 10b are switched to the side of the combustion air pipeline 15, thereby feeding combustion air to burner 1a and 1b by way of the heat reservoirs 10a and 10b while they are switched to the exhaust gas suction pipeline 16, thereby exhausting the combustion waste gas in the furnace outside the furnace by way of the heat reservoirs 10a and 10b. Since the heat reservoirs 10a and 10b are furnished with a function of a switching valve between the combustion air side and the exhaust air suction side, there is on need to install an on/off valve on the way of the combustion air pipeline 15 and the waste gas suction pipeline 16. This construction makes it possible to reduce the size of equipment.