PURPOSE: To prevent the metal wall of a combustion chamber from being damaged by the high temperature of flame and the combustion temperature of combustibles from lowering by a structure wherein bimetals, each of which opens a plurality of openings, at high temperature and closes them at low temperature, are provided, through which openings air in air- cooled chambers is blasted in the combustion chamber.

CONSTITUTION: Metal walls 13 are provided on the lateral sides of a combustion chamber 3. Bimetals 18, each of which opens at high temperature and closes at low temperature, and provided at a plurality of openings, through which air in air-cooled chambers 14 provided at the back of each metal wall is blasted in the combustion chamber 3. Thus, when high calorie matter to be incinerated such as plastic or the like is fed, the bimetal 18 provided at an opening 17, which locates nearly the same position as said matter to be incinerated, opens with the temperature rise resulting from the combustion of said matter to be incinerated so as to blast more air in the air-cooled chamber 14 than from other opening, resulting in preventing the metal wall 13 from being partially heated up to high temperature. Further, the bimetal 18 provided at an opening 17, which locates nearly the same position as low calorie matter to be incinerated, closes with the temperature drop resulting from the combustion of the low calorie matter to be incinerated so as to blast less air in the air-cooled chamber 14 than from other opening, resulting in preventing the combustion temperature of the matter to be incinerated from lowering.