an axial portion of the lower case 28 of the inflator 24 and a squib not shown is disposed in this through hole 32 an unillustrated fire propagating agent is disposed immediately above the squib and a gas generating agent a coolant a filter and the like are accommodated around the squib it should be noted that the case where the squib is used is the case of the electric ignition type and an acceleration sensor is disposed in the case of the mechanical ignition type here a substantially fan shaped caution label 34 serving as an identifying means is bonded to the bottom surface of the lower case 28 of the above described inflator 24 the caution label 34 has a two layered structure comprising an upper label layer 36 serving as a shape changing member and a lower label layer 38 serving as a display member usual handling precautions i e instructions concerning the air bag 10 in an unactuated state e g 34 do not heat 34 are written on the upper label layer 36 this upper label layer 36 is made of a material which shrinks at about 100 u00b0 c e g a polystyrene based film material meanwhile the fact that the inflator 24 has been actuated and appropriate information for reutilization e g 34 air bag has been actuated 34 and the types of metal used as useful information for reutilization are written on the lower label layer 38 in addition this lower label layer 38 is made of a material which allows the written notes to be readable even at about 180 u00b0 c e g a polyester based film.