An apparatus (20) for inflating an inflatable vehicle occupant protection device (22) comprises a container (60) which defines a chamber (62) for storing gas for inflating the protection device. Fluid is in the chamber (62) and comprises a combustible fuel gas. The container (60) includes an inner housing (64) comprising an inner member (80) extending along an axis (A). The inner member (80) has a first surface portion defining the chamber (62). A second surface portion (180) of the inner member 80 defines at least a portion of the periphery of the inner member (80) extending along the axis (A). An outer housing (66) comprises an outer member (84) with a third surface portion (182) engaging and supporting the second surface portion (180) of the inner member (40) over its axial and circumferential extent. An igniter (100) ignites the fuel gas to create heat. An opening (220) in the outer housing (66) directs gas from the chamber (62) to inflate the protection device (22).