Non-return valves are essential on welding and cutting equipment for user safety and protection of the installation: The best combination is to fit a pair of flame arrestor non-return valves (European standard EN 730-1) on the torch or as close as possible to the user, AND a pair of flame arrestor non-return valves (European standard EN 730-1) on the relief valve. It should be noted that the thermal flame arrestor non-return valves (standard EN730-1) offer the best performance, in particular on torches and/or relief valves when working in a confined space.