To clarify clothes worn in a clean room to a prescribed cleanliness level by actuating a device by a controller so as to remove the particulate till a desired particulate level based on the output of a particulate counting assembly.

A drying system 10 is provided with a dryer control unit 20, a dryer 30, a particulate counting device 40, and a measuring sampling pump 50. The particulate counting device 40 which is provided in the dryer is so constituted that an air sample is extracted from a dyer exhaust duct 34 of the dryer 30 to the particulate counting device 40 via a sampling line 42. This particulate counting device 40 outputs an analog or digital output signal 46 expressing the measured particulate level to a dryer control unit 20. The dryer control unit 20 utilizes the output signal 46 for an operation control of the dryer 30 and continues the drying operation till the measured particulate is lowered to the prescribed concentration or less.