Abstract: A flame arrestor device capable of checking flashback when incorporated in a system utilizing one or more detonatable gases under pressure for controlled energy release purposes, the device being generally installed in series having one or more gas sources upstream while gas conducting means and ignition means are arranged downstream of a membrane barrier mounted and secured to a supporting means which is, in turn, mounted within an arrestor housing with provision for gaps of limited size on the upstream and downstream side of the membrane barrier to permit gas flow. The invention includes built in or separate ignition means downstream of the membrane barrier.