An image forming apparatus having: a filter member configured to trap particles floating in the apparatus; a suction section configured to suck air including the particles at a variable suction rate; a determiner configured to determine the suction rate of the suction section; an exhaust path capable of leading the air sucked by the suction section to outside of the apparatus through the filter member; a circulation path capable of allowing the air sucked by the suction section and passing through the filter member to circulate inside the apparatus; a switching member configured to make switches between the exhaust path and the circulation path; and a control unit configured to control at least the suction section and the switching member. The control unit allows the switching member to open the exhaust path only when the suction rate determined by the determiner is equal to or less than a predetermined value.