PURPOSE: To clean a dust-proof filter on the front side of a fan for forced air cooling of electronic apparatus by running the fan backward for a specified time then running the same forward in the stage of supplying a power to the fan.

CONSTITUTION: A fan F is run backward for a specified time in the stage of supplying a power source thereto. Air flows toward a filter FIL and removes the dust sticking to the filter FIL. The scattering of the dust is prevented by a suction device COM. The fan F is run forward upon lapse of a specified time. The contamination of the filter is decreased and the interval of maintenance work is prolonged.