ISO 5175-1:2017

ISO 5175-1:2017 specifies the general requirements and tests for safety devices for fuel gases and oxygen or compressed air incorporating a flame (flashback) arrestor used downstream of manifold, cylinder and/or pipeline outlet regulators, and upstream of blowpipes for welding, cutting and allied processes.
ISO 5175-1:2017 does not specify the location of these devices in the gas system.
ISO 5175-1:2017 is not applicable to safety devices not incorporating a flame arrestor, covered by ISO 5175-2.
ISO 5175-1:2017 does not apply to the use of safety devices incorporating flame arrestors for applications with premixed oxy/fuel or air/fuel gas supply systems, e.g. downstream of gas mixers or a generator to produce hydrogen/oxygen mixture by electrolytic decomposition of water.