A dual stage inflator for an inflatable vehicle safety device, the dual stage inflator comprising: a housing defining a first chamber containing a first gas generant material; an ignitor cup disposed in the first chamber and defining an interior containing an ignitor material; a first ignitor device extending into the interior of the ignitor cup; a combustion cup and a lid disposed in the first chamber and cooperating to define a second chamber containing a second gas generant material, the combustion cup including a cup sidewall extending between a first axial end and a second axial end, the first axial end being an open end, the lid normally in a closed position relative to the combustion cup to close the open end of the combustion cup, the lid moveable away from the combustion cup in response to an increase of pressure within the combustion cup for venting combustion gas out of the combustion cup; and a second ignitor device extending into the combustion cup and closing the second axial end of the combustion cup; wherein: the combustion cup includes a first axially extending portion adjacent the first axial end having a first outer diameter and a second axially extending portion adjacent the second axial end having a second outer diameter, the first outer diameter being less than the second outer diameter, and wherein the lid includes a lid sidewall extending in an axial direction and radially overlapping at least a portion of the combustion cup including the first outer diameter, wherein the dual stage inflator comprises a filter arranged radially between the cup sidewall and the housing, characterized in that the lid sidewall has a thickness in a radial direction, the second axially extending portion of the combustion cup being positioned closer to the filter in the radial direction than the thickness of the lid sidewall. a housing defining a first chamber containing a first gas generant material; an ignitor cup disposed in the first chamber and defining an interior containing an ignitor material; a first ignitor device extending into the interior of the ignitor cup; a combustion cup and a lid disposed in the first chamber and cooperating to define a second chamber containing a second gas generant material, the combustion cup including a cup sidewall extending between a first axial end and a second axial end, the first axial end being an open end, the lid normally in a closed position relative to the combustion cup to close the open end of the combustion cup, the lid moveable away from the combustion cup in response to an increase of pressure within the combustion cup for venting combustion gas out of the combustion cup; and a second ignitor device extending into the combustion cup and closing the second axial end of the combustion cup; wherein: the combustion cup includes a first axially extending portion adjacent the first axial end having a first outer diameter and a second axially extending portion adjacent the second axial end having a second outer diameter, the first outer diameter being less than the second outer diameter, and wherein the lid includes a lid sidewall extending in an axial direction and radially overlapping at least a portion of the combustion cup including the first outer diameter, wherein the dual stage inflator comprises a filter arranged radially between the cup sidewall and the housing, characterized in that the lid sidewall has a thickness in a radial direction, the second axially extending portion of the combustion cup being positioned closer to the filter in the radial direction than the thickness of the lid sidewall. the combustion cup includes a first axially extending portion adjacent the first axial end having a first outer diameter and a second axially extending portion adjacent the second axial end having a second outer diameter, the first outer diameter being less than the second outer diameter, and wherein the lid includes a lid sidewall extending in an axial direction and radially overlapping at least a portion of the combustion cup including the first outer diameter, wherein the dual stage inflator comprises a filter arranged radially between the cup sidewall and the housing, characterized in that the lid sidewall has a thickness in a radial direction, the second axially extending portion of the combustion cup being positioned closer to the filter in the radial direction than the thickness of the lid sidewall.