or may be a membrane nitrogen generator when purge gas generator 21 is a membrane nitrogen generator there is generated nitrogen gas having a nitrogen concentration within the range of from 90 to 99 mole percent in the embodiment illustrated in fig3 nitrogen gas is withdrawn from membrane nitrogen generator 21 in stream 22 and passed to a gas contaminant cleaning system which in the embodiment illustrated in fig3 is ejector 23 an ejector is a device that uses a high energy fluid stream to entrain or move a second lower energy fluid stream the ejector produces a mixed stream with an energy level in between that of the first and second fluid such that energy is conserved and with a mass flow rate of the first and second fluids combined the first high energy fluid stream enters the ejector converging nozzle this causes the velocity of that first stream to increase at the expense of pressure the stream then enters the mixing chamber where a low pressure region is created due to the momentum and viscous forces created by the first stream this low pressure region is used to draw the second lower energy stream into the mixing chamber the two fluids are mixed in the process the mixed fluid then exits the mixing chamber and enter a diffuser where fluid pressure is recovered at the expense of velocity nitrogen gas from ejector 23 is passed in line 24 to heat exchanger 25 wherein.