An inflator for an air-bag comprises at least one gas bottle (1, 2) containing pressurized gas. The gas bottle is sealed by a rupturable foil (9). There is a support member (15) engaging the rupturable foil to maintain it in an unruptured state. The support member (15) is retained in an initial position by a part (23) of a piston element (20) which directly engages the support member (15). The piston element (20) is associated with a squib (11) to drive the piston element from an initial position to a release position in which the piston element no longer engages the support member (15). This permits the support member (15) to move to a position in which the foil (9) will rupture to permit gas to escape from the bottle. The preferred embodiment has two gas bottles each sealed by a respective foil each maintained by a support member which directly engages a single piston member.