NOVELTY - Method of recovering a rare gas from a mixed gas stream comprises: determining the amount of rare gas in the mixed gas stream at different times during a cyclical process; exhausting the mixed gas stream through a waste gas abatement process when the determined amount of rare gas in the mixed gas stream is below a predetermined level; and treating the mixed gas stream in a rare gas separation and recovery process when the determined amount of rare gas in the mixed gas stream is above the predetermined level.    USE - The method is useful for the recovery of rare gas, preferably helium from a mixed gas stream and mixed exhaust gas from a semiconductor processing chamber (all claimed). The method is useful for processes including LCD, flat panel production, solar cell production, glass coating and for processes that require the use of helium in large quantities.    ADVANTAGE - The method provides a process, where all exhaust gas is passed through the rare gas recovery lines (where there is enough rare gas at any given time to warrant separation and recovery), thus the method is feasible and economically viable. The method recovers and reuses significant amount of helium, thus reduces the amount of fresh helium required to carry out processes and process costs. The recovered helium can be sold commercially providing an income stream, hence reduces the overall costs.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) an apparatus for separating a rare gas from a mixed gas stream comprising: at least one load lock chamber having an inlet door and an outlet door for introduction and removal of a substrate to be treated and a waste gas exhaust; a rare gas supply source in communication with the load lock chamber; a purge gas supply source in communication with the load lock chamber; and a waste gas treatment system in communication with the waste gas exhaust comprising a waste gas abatement system, a rare gas recovery system, and switch means to send the mixed gas stream exiting the load lock chamber to either the waste gas abatement system or the rare gas recovery system based on the amount of rare gas present in the mixed gas stream at any given time during a process carried out on the substrate; and    (2) a method of recovering rare gas from a mixed exhaust gas from a semiconductor processing chamber, comprising: inserting a substrate into the processing chamber; evacuating the processing chamber; treating the substrate according to a desired semiconductor device attribute; introducing cooling rare gas to the chamber to cool the substrate; exhausting mixed exhaust gas from the chamber through a rare gas recycling system; introducing purge gas to the chamber; exhausting further mixed exhaust gas from the chamber through a waste gas abatement system; and removing the substrate from the chamber.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a system for the recovery of helium from the waste gas of a cluster tool.    General exhaust system (300)    Compressor/blower unit (320)    Buffer tank (340)    Purification unit (360)    Helium liquefier (380)