These requirements cover tank vent deflagration flame arresters and in-line detonation flame arresters. The requirements for tank vent deflagration flame arresters cover arresters for use on vents of storage tanks for petroleum oil and gasoline. These flame arresters are intended to prevent propagation of flame into the storage tank. Combination flame arrester-vent valves are also covered. The requirements for in-line detonation flame arresters cover arresters for use in piping systems containing flammable vapors and gases in mixture with air. These flame arresters are unidirectional or bidirectional and are intended to prevent the transmission of detonation and deflagration.