Large quantities of high purity and high pressure nitrogen or oxygen gas are produced using a portable system. A PSA, VSA, TSA, or permeable membrane system cleans the air of water and carbon dioxide, as normally required by the cryogenic distillation cycle, but additionally, a significant amount of the oxygen or nitrogen is also removed, depending on the desired produced gas. The removal of the oxygen or nitrogen before the cryogenic process permits the distillation column to be significantly shorter than would otherwise be required. This in turn reduces the size of the equipment such that it can easily be transported and setup. Additionally, a high pressure liquid pump is used to boost the pressure of the nitrogen or oxygen immediately before it goes through the last pass of the cryogenic heat exchanger where the liquid is vaporized and the incoming gas is cooled.