Abstract: The invention relates to an air extraction apparatus for conditioning air in an enclosed space wherein the air in said enclosed space is stratified due to a temperature gradient between a ceiling and floor of the enclosed space. The apparatus includes a conduit having an inlet end and an outlet end, the conduit adapted to be arranged and installed with its outlet end in communication with an opening in a wall of the enclosure and its inlet end in proximity to the floor when in use. A fan means is located in the conduit to effect movement of air from the floor level of the enclosure through the inlet end to and outwardly of the outlet end. A control means is attached to the conduit and is associated with the fan means to selectively connect the fan means to a source of power, the control means being responsive to a selected condition e.g. relative humidity of the air in the enclosure.