PURPOSE: To prevent an offensive a smell from filling in a chamber, because a ventilator does not work or an exhaust tube is broken, by providing a shut-off valve operated by the differential pressure in and out of the chamber which is filled with a heated body.

CONSTITUTION: When a combustion material 6 for ignition is put on the upper stage of an equipment and a ventilating fan 7 is operated, the pressure in a chamber filled with the heated body 8 is lowered to produce the difference in pressure between the outside of the chamber and the inside thereof, so that a shut-off valve 2 which is normally settled on a valve seat 3 is floated up by a ventilating material 1, feeding the secondary air coming into a chamber from a vent 4 provided to a top lid 5 to the combustion material 6 to continue a normal combustion. If a ventilator 7 is stopped, the pressure in a chamber filled with the heated body 8 and that out of a chamber is made uniform, then, a shut-off valve 2 is settled an a valve seat 3 under the own weight thereof, at the same time, the secondary air being supplied to the combustion material 6 is shut-off, as a result, the flame on the combustion material 6 is extinguished.