An assembly is described, including a filter disposed downstream from a freeze dryer chamber, a first valve and a second valve disposed downstream from the filter, and a gauge disposed downstream from the first valve. A method is described, including maintaining a first valve of a circuit in a closed position during a steam sterilization cycle, maintaining the second valve in an open position during the steam sterilization cycle, receiving, from the gauge, a plurality of pressure measurements, and determining, by a processing device, an endpoint of a primary drying stage. The circuit includes the filter, the first valve, the second valve, and the gauge. A freeze-drying system is described, including a freeze dryer chamber including one or more orifices in fluid communication with the freeze dryer chamber and a circuit coupled to the freeze dryer chamber via a first orifice.
