The heat energy contained in the process exhaust air is transferred directly to the outdoor supply air. A separate supply air unit is no longer needed. The heat exchanger is aluminium-made and oil-proof to avoid a material exchange between discharged and fed air. ProTERM is flexible (as pictured) in normal or mixed operation with circulating air for cooling in summer and heating in winter, or in pure air recirculation. Environmental protection that pays off. The sizable savings become apparent when compared with the annual heated air demand.