PURPOSE: To automaticaly detect the insufficent deodorizing capacity of a deodorizing apparatus in the titled apparatus such as a diazo type copier or the like, by a method wherein power consumption of a heater within a definite time is detected and the detected value is compared to a reference value.

CONSTITUTION: A relay 17 and relay contacts 17a, 17b are provided so as not to operate an integrator 18 until an inside of a catalyst tank is reached to set temp. after operation of a deodorizing apparatus is initiated. When temp. of the tank inside is lowered after temp. of the tank inside is lowered to the set temp. a thermostat 15 is closed to shut off current supply of a relay 16 and a relay contact 16b is closed to supply current to a resistor 19. The integrator 18 integrates voltage generated at both ends of the resistor 19 to issue output of an integrated value. When a catalyst in the deodorizing apparatus is poisoned and the deodorizing capacity thereof is lowered, generation of reaction heat in the catalyst tank is reduced and power consumption of a heater 14 is increased. Because a current supply time to the heater 14 is lengthened, the integrated value in a definite time is gradually increased and, when the integrated value is reached to the reference value, a comparator 22 issues output to operate an alarm means 24 and the insufficiency of deodorizing capacity is informed.