A rupture feature releases pressurized gas into a diffuser through an egress opening in an inflator wall responsive to a pressure impulse in the inflator. A sturdy rupture fragment is positioned opposite the egress opening. A thin rupture membrane continuously circumscribes and sealingly interconnects the rupture fragment to the inflator about the egress opening. Rupture membrane thickness is less than rupture fragment thickness or inflator wall thickness at the egress opening. The rupture membrane is upstanding from the inflator wall about the egress opening to a constant height. The rupture fragment and the rupture membrane are integrally-formed with each other and with the inflator wall at the egress opening. The pressure impulse impacts the rupture fragment, urges the rupture fragment away from the inflator, detaches the rupture fragment from the inflator by fully transversely fracturing the rupture membrane, and drives the rupture fragment into containment within the diffuser.