Benefits Stops the pressure front and flame front. Stops gas from back feeding into the system. Prevents fire from being supported by gas. Signal lever will show if the pressure sensitive cut-off has been activated; the lever is also used for resetting the flashback arrestor. Unitor W-66S Oxygen is the No. 1 choice for Flame Arrestors (Flashback Arrestors) certified and under surveillance by The Federal Institute for Materials Research and Testing (German: Bundesanstalt fr Materialforschung und -prfung, or BAM) and OCIMF/RIGHTSHIP compliant. The Wilhelmsen W-66S protects regulators and gas cylinders against flashback and detonation. Maritime authorities, such as the Norwegian Maritime Directorate, require the installation of flashback arrestors for acetylene and oxygen to prevent flashbacks. Flashbacks can occur when incorrect maintenance or use of gas welding equipment causes a flame to travel back through the hoses and into the regulator or cylinder. This can lead to an explosion