the first portion 34 of the bore is cup shaped element 39 having a generally cylindrical portion with a tubular wall 40 of a diameter slightly less than the diameter of the portion 34 of the bore the cylindrical portion 40 terminating with a closure 41 of a shape corresponding to the shape of the inwardly directed neck 35 a plurality of apertures 42 are formed at appropriate positions in the tubular side wall defining the cylindrical portion 40 of the cup shaped element 39 a channel 43 is defined between the cup 39 and the wall defining the bore 34 35 contained within the cup is a pyrotechnic material 44 which may be the same as the pyrotechnic material of fig1 the cup has a lower open end which is initially sealed by means of a membrane 45 which simply serves to retain the pyrotechnic material within the cup the membrane 45 serves to separate the interior of the cup from a distribution plenum chamber 46 which is associated with three outlet ports 47 48 and 49 the being closed by detonation plate 50 51 and 52 respectively it is envisaged that when the embodiment of fig2 is to be activated a shock pulse will pass down the shock tube 32 into the chamber 28 and ignite the relay pyrotechnic charge 30 the membrane 29 will be ruptured and the shock pulse will pass through the membrane 37 to ignite the receptor pyrotechnic charge 38 within the portion 36 of relatively small diameter of the bore within the housing 33 the shock and or flame from the receptor pyrotechnic charge 36 will flow down the passage 43 between the cup 39 and the inner wall of the bore.