Nitrogen Generators provide two way of generating nitrogen. In one approach, compressed air passes across a semi-permeable membrane that allows nitrogen to permeate and almost completely impedes the transfer of other air components and contaminants at high flow rates. The second approach is a two stage process that uses two adsorption beds of carbon molecular sieves. Air enters the front of the cylinder and as it passes through the cylinder, it is separated in to oxygen and nitrogen. The nitrogen is allowed to move out of the first bed until the oxygen nears the end of the carbon bed. At this point the flow is reversed in the cylinder and nitrogen coming off the second cylinder is allowed to purge the first cylinder. This process is called pressure swing adsorption. Alternatively both cylinders are charged with air and provide nitrogen. The nitrogen is used to both purge and reverse flow the cylinder being cleaned and to provide nitrogen for analytical purposes. Additional purification is still required and hence passing the nitrogen leaving the generator through supplemental purifiers can reduce the oxygen, carbon dioxide and water levels in the nitrogen even lower than the sub parts per million levels supplied by the generator.