Abstract: The gas generator according to the present invention is characterized by a combustion chamber formed with a combustor cup (14) having an annular top wall fixed at an inner edge portion thereof to a circumferential edge of a top wall of a central cylindrical holder (4) by riveting (28). A combustor plate (16) is welded at an outer edge thereof to an inner edge portion of a longitudinal extension of the combustor cup (14), and at an inner edge thereof to a bottom edge portion of the holder, so as to close the combustion chamber. A diffuser (12) is provided to cover the top wall of the central cylindrical holder (4) and the top wall of the combustor cup to form a double wall of the combustion chamber. A flange extends from the longitudinal extension of the combustion cup, the flange being welded to the inner wall of the extended portion of the diffuser to form a filter/cooling chamber.