Apparatus (130) for use in wound therapy of mammals is described, the apparatus (130) comprising: a dressing covering the wound, the dressing being substantially sealed to prevent ingress of ambient atmospheric air to the wound; aspiration means (132) operably connected to a space between the dressing and the wound by an aspiration conduit (142) sealed to the point of entry between wound and dressing against ingress of ambient atmosphere, said conduit (142) being for aspiration of said wound and for removal of fluid from said space between said wound and said dressing; a waste container (148) for receiving aspirated fluid to be discarded operably connected to said aspiration conduit; and heating means (144) for heating said fluid in order to increase the vapor pressure thereof and to cause evaporation to reduce the volume of the fluid in the waste container (148). In a preferred embodiment of the present invention the waste fluid is also provided with a sparge gas.