The accidental ignition of flammable gases or vapors from vent pipes of storage tank or process vessel presents a constant threat to plant and personnel. The use of flame arresters is one of the essential measures taken to avoid or minimize the possible consequences. Their application is widespread, ranging from the protection of small solvent tanks to the safety of large and complex process plant. The oil, gas, petroleum, chemical and petrochemical industries are major users. A flame arrester is a static device which stops a flame entering into the storage tank or process vessel containing a flammable gas or vapor. An end-of-line type flame arrester is fitted at the extreme downstream end of a pipeline. The arrester consists of a flame quenching, element contained within a housing which incorporates thread or flange connections for fitting to pipework. The element is often of greater diameter than the pipework in order to compensate for pressure drop and therefore the housing is enlarged accordingly.