PURPOSE: To prevent abnormal rise in the temperature of vaporizer and burner unit by an arrangement wherein whenever an abnormality such as breaking of a temperature sensing thermistor, etc. occurs only burner motor is actuated for a preset time after the detection of the abnormality and the whole operation is stopped after cooling of the vaporizer and burner unit.

CONSTITUTION: When an abnormality such as breaking of a temperature sensing thermistor 2 adapted to sense the temperature of the vaporizer and burner unit, etc. occurs, only the burner motor is turned ON while a times circuit 21 reaches its preset time and then a timer circuit 26 reaches its preset time thus cooling the vaporizer and burner unit. Subsequently, a reset switch 42 is turned ON to apply an electric current to a resetting coil 32 to close a contact 42. Then, the same operation is repeated to apply an electric current again to a vaporizing heater. Because the vaporizer and burner unit is cooled, however, even in case of the second application of electric current to the vaporizing heater, no abnormal rise in temperature occurs and the operation is stopped after a predetermined time.