An image forming apparatus is provided that includes an image forming unit disposed in a main body and configured to form an image on a recording medium, an output tray provided in the main body and configured to receive the recording medium having an image formed thereon, and an ejection device provided in the main body and configured to eject the recording medium to the output tray. A plurality of pinch valves are provided to control flow of material into and out of the pump chamber. The insulating member is coupled between the housing and the central sensor electrode assembly. In a preferred embodiment of the present invention, said quantity of regeneration heat is also adjusted as a function of the water content of the feed gas.