Abstract: A tank has a base, corrugated side walls structurally mounted directly to the base, the corrugated side walls and the base defining a tank interior, the corrugated side walls having a trough and a crest; the trough being spaced within the inner tank receptacle relative to the crest; and a roof plate above the tank interior, the roof plate being structurally mounted to the corrugated side walls opposite the base. An inner tank may be inserted into the tank, the inner tank having a plurality of rigid or semi-rigid panels that are attached directly to adjacent panels to form a bottom wall and inner side walls of the inner tank.

Abstract: An air transfer apparatus which includes a door frame having a top, a bottom and opposed sides. The top, bottom and opposed sides define a door receiving cavity. A door is positioned within the door receiving cavity. The door is pivotally mounted to one of the opposed sides of the door frame for pivotal movement between an open and a closed position. The door has a first face and a second face. At least one fan is positioned in the door. The fan is adapted to either move air from the first face to the second face or from the second face to the first face. Preferably, the door is manufactured so it can be mounted with either side to the left or right and either end at the top or the bottom, so as to accommodate any conceivable installation.