Since 1985 in a step by step approach an advanced air revitalisation system has been developed for a crewed spacecraft. The metabolically produced carbon dioxide is concentrated through a solid amine water steam desorp-tion system and reduced to water and methane in a so-called Sabatier reactor. The water is currently fed into a fixed alkaline electrolyser to reclaim the oxygen for the crew. However, also water from other sources may be used. The hydrogen is recycled into the Sabatier reactor. The present system handles methane as a waste product closing so far the oxygen loop only. The system has been already successfully demonstrated in a laboratory scale configuration for a crew of three persons in 1996/1997.This paper discusses the results of the current development phase in which the system is reconfigured to fit into an International Space Station payload rack (ISPR). For this purpose the complete system design has been reviewed and upgraded where necessary. In particularly, a complete new Sabatier reactor design has been established, introducing the highly active, newly developed catalyst and the carbon dioxide absorber system has been redesigned. The new system configuration has been subjected to intensive testing.The effort intents to demonstrate the technology readiness for a possible implementation in the ISS enhancement programme and has been performed under contract of the European Space Agency.