preferred so that in the event of self sealing and self extinguishment a given battery vent will still retain its venting capabilities more particularly it is believed that two slits per cell is the preferred minimum in order to provide substantial margin of safety in the event that the venting means is subjected to numerous exposures to ignition another advantage of the present invention is the provision of venting means which are self sealing when exposed to a persistent flame this characteristic is accomplished by constructing at least a portion of the material surrounding the slit from a meltable material such as polypropylene and copolymers thereof which is meltable and which responds to a persistent flame by melting to close or seal the slit and to thereby extinguish the flame by cutting off the fuel gas which is being supplied to the flame through the slit it is important during this melting process to ensure that no portion of the slit increases in width beyond the size of 0 007 inches and more preferably is maintained within the range of 0 004 to 0 005 plus or minus 0 001 inches in the event that the melting of material surrounding the slit should act to enlarge the slit width over the aforementioned dimensions a spark or flame from the not yet fully extinguished.