In the interior of treating chamber, fruit containers of plastics with perforated bottom are stacked onto a pallet up to several layers thereby forming a chimney-shaped processing space (hereafter referred to as ‘chimney’). This chimney is covered with a bell-shaped hood having an axial fan on top. By running axial fan, the chimney turns into a differential pressure unit. The panel type system consists of plural number of differential pressure units accommodated in a panelized treatment chamber which is provided with temperature and humidity conditioned air by forced circulation.