An example of an inflatable seal for a door includes a bi-directional airflow pattern of frost-inhibiting heated air. The bi-directional flow pattern enables the seal's discharge opening and supply air blower to both be located well above the floor and preferably above the doorway. If the discharge opening is near the suction inlet of the blower, such an arrangement makes it possible to recover previously heated air by returning some of the warm air back to the blower. In some examples, the seal includes a supply air conduit and a return air conduit with one disposed within the other. The internal conduit may include a relatively stiff elbow to prevent that conduit from becoming kinked near an upper corner of the door.