Apparatus for treatment of products comprising a product carrying unit (4) extending along a longitudinal product conveying direction and being provided with a plurality of openings adapted to allow an upwardly directed flow of gas through said openings and past the products. The apparatus further comprising a gas treatment means (10-1) and a gas circulation means (20,22,24,26). The apparatus being characterized by a first compartment adapted to guide the flow of gas from the carrying unit down along a first side of the treatment means (10-1), the treatment means having an inlet at a first level and an outlet at a second level, the second level being higher than the first level, thereby providing an upwardly directed flow of gas through the treatment means. The apparatus is further characterized by the circulation means (20,22,24,26) being adapted to draw the gas from the outlet downwardly along a second outer side of the treatment means (10-1), transversely opposite to the first side, and to provide the upwardly directed flow of gas through the openings of the carrying unit (4).