Modular cartridges which may be inserted into and removed from a well or receptacle on the bottom of a pod. The cartridges may be configured to include various types and combinations of valves, filters, and/or conditioning agents. A standalone cartridge replacement station may be provided for inserting and removing various cartridges from one or more of the receptacles on the bottom of a pod while wafers are seated within the pod. The standalone replacement unit may decouple an existing cartridge from the pod by rotating the cartridge from a locked to an unlocked position and then lowering the cartridge out of the pod. Thereafter, the replacement station may insert a new cartridge up into the appropriate receptacle and rotate the cartridge into a locked position in the pod.