Abstract: A freeze-drying apparatus has a freeze-drying chamber, a double-walled product shelf disposed within the freeze-drying chamber, a conduit system partially disposed within the freeze-drying chamber and attached to the product shelf for temperature regulation thereof, a heat-exchange fluid contained in the conduit system, a test gas reservoir connected to the conduit system outside of the freeze-drying chamber, and a test gas specific detector connected to the chamber for detecting test gas introduced into the freeze-drying chamber from the heat-exchange fluid through a leak in the conduit system. In the alternative, the test gas reservoir is connected to the freeze-drying chamber, and a test gas specific detector is connected to the conduit system outside the freeze-drying chamber for detecting test gas introduced into the heat exchange fluid from the freeze-drying chamber through a leak in the conduit system.