To conduct an operation for 24 hours, day and night, without causing noise pollution by installing an air suction valve between an air feed blower and a header pipe for sending air or an air box.

In a day time period, and air suction valve 7 is closed and an air feed blower 3 is operated to effect a forced draft so that air is fed into a furnace 1 from an air blowoff pipe 2 through a header pipe 4 or air box and a waste 9 to be incinerated in the incinerator 1 is burnt by a forced draft. In a night time period, the valve 7 is opened and the blower 3 is stopped so that air is drawn from the valve 7 by a suction force caused by a draft of a stack into the incinerator 1 from an air blowoff pipe 2 through the header pipe 4 or air box, whereby the waste 9 in the incinerator 1 is burnt by an induced draft. Thus a forced draft or an induced draft can be selected and an operation can be performed according to the level of noise so that the rate of operation can be improved and 24-hour operation per day can be achieved.