Abstract: An apparatus for use in inflating an inflatable vehicle occupant restraint (12) comprises a grain (110) of ignitable gas generating material which, when ignited, generates gas for inflating the vehicle occupant restraint (12). The grain (110) of gas generating material has a surface portion defining a cavity (124) in the grain (110). The apparatus further includes a plug (160) of pyrotechnic material which is more readily ignitable than the gas generating material. The plug (160) of pyrotechnic material, when ignited, produces and emits combustion products which ignite the grain (110) of gas generating material. The plug (160) of pyrotechnic material is located in the cavity (124) in the grain (110) of gas generating material.