A gas generator construction particularly for the inflation of inflatable protective bags which are used in safety systems of vehicles comprises a housing with a central tubular housing part which contains an ignition device that is surrounded by a reaction chamber containing a gas generating charge which in turn is surrounded by an outer filter housing. The gases which are generated in the reaction chamber are directed through openings and into the filter housing and then outwardly through slots of the filter housing for use in expanding the protective bag. The reaction chamber and the filter chamber are formed by an annular substantially S-shaped wall member which has a bottom forming wall portion for the reaction chamber which is joined to the central tubular part, for example, by welding. The S-shaped wall member includes a division wall between the reaction chamber and the filter chamber and an outer casing portion forming a cylindrical outer wall which is connected to the division wall between the two chambers by a curved web portion of the S-shaped wall. A dome shaped cover is employed to enclose the reaction chamber and a cover ring is used to enclose the filter housing. Each are connected to the intermediate wall portion of the S-shaped member.