Inflator for a passive vehicle safety device

A dual stage inflator includes a housing defining an internal cavity including a combustion chamber. The combustion chamber includes a first portion having a first gas generant material separated from a second portion having a second gas generant material. A gas generant retaining wall is disposed in the housing. A first stage ignition device is disposed in the first portion of the combustion chamber. A second stage ignition device is disposed in the second portion of the combustion chamber. A lid normally closes the second portion of the combustion chamber and is spaced from the gas generant retaining wall. The lid is moveable to an open position opening the second portion of the internal cavity to release combustion gas and abutting the gas generant retaining wall in response to an increase of pressure within the second portion of the combustion chamber. An outer side of the lid and the adjacent side of the gas generant retaining wall are cooperatively configured to allow a flow of combustion gas between the gas generant retaining wall and the lid when the lid abuts the gas generant retaining wall in the open position.