Gas separation tests were performed with nitrogen containing small concentrations of deuterium or tritium on a small-scale polyimide membrane module purchased from Ube Industries, similar to that developed at the Japan Atomic Energy Research Institute (JAERI). Experimental results showed that this separation process could be potentially applied to tritium removal systems used in tritium handling facilities. It would allow to reduce significantly the gas volume to be treated by the conventional oxidation-adsorption process, and, therefore, the number or size of associated equipments. Hazards arising from handling of highly toxic tritiated water vapor due to conversion of elemental tritium, would hence be lowered.