PURPOSE: To arrange so as not to give unpleasant feeling to passengers in rear seats by changing over the number of revolution of a motor by means of a temperature switch from a predetermined temperature of a component, thereby weakening air flow in the component when the temperature therein is low.

CONSTITUTION: A fan 21 is driven by a motor 13 to purify influent air by means of a filler 22, etc. The motor 13 is controlled by providing a plurality of semiconductors 15, 17 for driving which are driven using electric current of different electric energy to change over said semiconductors 15, 17 by means of temperature switch 18 from a predetermined temperature. Consequently, when the temperature in a component is lower than the predetermined temperature, air flow therein can be weakened; therefore, unpleasant feeling of passengers in the rear seats of a car caused by air flow running against their heads can be eliminated, whereby the interior of the component can always be purified by operating an air purifier independent of the temperature therein.