This International Standard specifies the requirements for flame arresters that prevent flame transmission when explosive gas-air or vapour-air mixtures are present. It establishes uniform principles for the classification, basic construction and information for use, including the marking of flame arresters, and specifies test methods to verify the safety requirements and determine safe limits of use. This International Standard is valid for pressures ranging from 80 kPa to 160 kPa and temperatures ranging from −20 °C to +150 °C. NOTE 1 In designing and testing flame arresters for operation under conditions other than those specified above, this International Standard can be used as a guide. However, additional testing related specifically to the intended conditions of use is advisable. This is particularly important when high temperatures and pressures are applied. The test mixtures might need to be modified in these cases. This International Standard is not applicable to the following: - external safety-related measurement and control equipment that might be required to keep the operational conditions within the established safe limits; NOTE 2 Integrated measurement and control equipment, such as integrated temperature and flame sensors as well as parts which, for example, intentionally melt (retaining pin), burn away (weather hoods) or bend (bimetallic strips), is within the scope of this International Standard. - flame arresters used for explosive mixtures of vapours and gases, which tend to self-decompose (e.g. acetylene) or which are chemically unstable; - flame arresters used for carbon disulphide, due to its special properties; - flame arresters whose intended use is for mixtures other than gas-air or vapour-air mixtures (e.g. higher oxygen-nitrogen ratio, chlorine as oxidant, etc.); - flame arrester test procedures for internal-combustion compression ignition engines; - fast acting valves, extinguishing systems and other explosion isolating systems; - flame arresters integrated or combined with explosion-protected equipment, such as blowers, fans, compressors and pumps.