PURPOSE: To eliminate the case in which the combustion stops by the existence of an obstacle and improve the easiness of use by providing on the back face and side edge section of a set-up foot on one side a passing air opening which connects an air space held by the set-up foot and the inside of a room and a temperature sensing element at a position to which the air from the passing air opening advances.

CONSTITUTION: Between the floor face F for installation and the lower section of the main body 1 there is a space S held by right and left setting feet 3. The space S opens at its front face which faces an indoor air intake port 2 into a room. An air passage opening 6 which connects the space S with the indoor is provided at the end section 4 of the back face of one of the setting feet 3 and a temperature detection element 7 in a control system to detect the temperature in the room and control a combustion device is provided at a position which is also exposed to the air from the air passage opening 6. Accordingly, if there is an obstacle in front and a shortcircuit of a low degree by hot air develops, it is mixed with the air in the room taken in from the air passage opening 6 so that air of temperature lower than that of the discharged hot air is taken in from the intake port 2 and the temperature detection element 7 also detects the air in the room the temperature of which has dropped, whereby the combustion does not stop and an adequate operation of the control system is realized.