Abstract: An incinerator includes a furnace body which confines a combustion chamber for receiving refuse therein and which has a bottom wall formed with a central opening, an ash release gate mounted pivotally to the bottom wall at the central opening, a stack which is provided on one side of the furnace body and which has a lower end part that is communicated with the combustion chamber adjacent to the bottom wall, and an exhaust port provided adjacent to an open top of the furnace body and operable so as to communicate the stack and the combustion chamber. A furnace cover is provided on the open top of the furnace body. First and second preheating tube arrangements are received in the lower part of the furnace body. The first preheating tube arrangement includes a plurality of upwardly extending concentric coil turns and has a surface formed with a plurality of air holes.