Abstract: A heat exchanger for the extraction and re-use of heat and/or moisture from gas flows comprising: a housing (3) forming a duct section for gas flows; a rotor (7) which has a plurality of air passages extending therethrough; and a guide arrangement (9, 10, 11) for carrying the rotor (7), which arrangement is movable laterally of the housing (3) to carry the rotor (7) between an inserted position and an at least partially extracted position. A drive (21) for driving the rotor (7) can be movable jointly with said rotor (7). In an expedient embodiment, the rotor bearing is located, optionally together with the drive, on a support member (10, 11) which is stiff against both torsion and bending and which is movable on guide rails. This support member extends expediently by means of two carrying members (10) next to the two major faces of said rotor (7), which are movable on said rails in the housing (3).