To provide an air cleaner having an ozone sensor, a smell sensor and a human detecting sensor, and a method for ON/OFF-operation of the air cleaner by combining these sensors.

The air cleaner is provided with the ozone sensor, the smell sensor and the human detecting sensor. The concentration of ozone, the presence or absence of odors and the presence or absence of persons are detected by imparting priority levels to these sensors, by which the air cleaner is operated or stopped and the operating state of the air cleaner is controlled. Accordingly, the air in buildings, rooms, vehicles, etc., can be cleaned more efficiently than by the conventional air cleaners, human errors can be prevented and the curtailment of costs, such as electricity expenses, is made possible as well.