In glass production, it is often necessary to preheat metal molds or tools so that the glass does not solidify too quickly or to keep thermal shock to an absolute minimum. Chamber furnaces with radiation heating or forced convection chamber furnaces are ideal for preheating such components. The furnaces are equipped with a lift door or parallel swing door that can be opened while the furnace is still hot. When opening, the hot side of the door swings away from the operator to ease working with the furnace.