DUAL STAGE INFLATOR

A dual stage inflator for an inflatable vehicle safety device including a housing defining a first chamber. The first chamber contains a first gas generant material. An ignitor cup is disposed in the first chamber and defines an interior containing an ignitor material. A first ignitor device extends into the interior of the ignitor cup. A combustion cup and a lid disposed in the first chamber cooperate to define a second chamber containing a second gas generant material. The combustion cup includes a cup sidewall and an open end. The lid is normally in a closed position relative to the cup sidewall to close the open end of the combustion cup and is moveable away from the cup sidewall in response to an increase of pressure within the combustion cup for venting combustion gas out of the combustion cup. A second ignitor device extends into the combustion cup. At least one of the lid and the cup sidewall includes an axially elongated venting geometry that is gradually revealed in response to movement of the lid away from the cup sidewall.