A method for stopping the propagation of ignited flammable gas in a conduit according to claim 11 further comprising the step of mounting a sensor means outside the inlet end of said conduit body for sensing the presence of {HEAD ~ said head portion} of {TAIL ~ said bullet means} when said bullet means has been deployed 
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A method for stopping the propagation of ignited flammable gas in a conduit according to claim 11 further comprising the step of mounting a sensor means outside the inlet end of said conduit body for sensing the presence of { HEAD ~ said head portion } of { TAIL ~ said bullet means } when said bullet means has been deployed
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