Abstract: A vacuum furnace having a single chamber in which a workpiece is supported and heat treated. A unique cooling system is designed for adaption with the low pressure/high volume radial flow fan which is positioned interiorly of the furnace adjacent the vertically uppermost portion of the chamber. The system includes an exhaust opening in the top of the chamber and a plurality of small openings strategically located in the lower half of the chamber for improving the uniformity of the flow pattern of cooled gas circulated upwardly through the chamber for cooling a workpiece positioned in the chamber.