Abstract : The exhaust gas in the future Tokamak demonstration reactor (DEMO) consists of more than 80 % of unburned fuel gas (D and T) with the balance being He, plasma enhancement gases (PEGs), and impurities. In DEMO we plan to recover the fuel gas (D and T) and PEGs. The paper focuses on the removal of He from the fuel gas and PEGs from the fusion reactors. Hence, the aim of the research is to test potential technologies to achieve this goal. In this paper, a carbon molecular sieve (CMS) membrane supplied by Tecnalia (Spain) is tested to remove the He along with D and T whilst retaining the PEGs.