A vehicle air-bag inflator includes a container initially containing a pressurised gas and having a vent opening in a wall thereof. A rupturable element, attached to a container wall, covers the vent opening, sealing the interior of the container. The rupturable element is attached to a first support, which supports a region of the rupturable element and prevents the rupturable element from rupturing. A first support, attached to a container wall, is movable between a first and a second configuration, with respect to the container wall. In an initial configuration, a second support supports the first support and prevents the first support from moving from a first configuration to a second configuration. In a final configuration, a second support allows the first support to move from the first configuration to the second configuration. An activation mechanism moves the second support from an initial configuration to a final configuration when triggered.