US Patent 10333119 Flame arrestor for a lead-acid battery

A lead-acid battery comprises a flame arrestor plug (1) for controlled venting of gases from the battery through the vent hole (3), wherein the flame arrestor plug has a valve element (5) for controlling the venting of gas from the vent hole and a plug portion (4) which is adjacent to or in contact with the battery casing (2) around the vent hole and which, together with the battery casing, defines a flow path through which gases released through the valve element can escape from the battery, at least a portion of the flow path being of sufficiently narrow cross-section to prevent propagation of a flame along the flow path.