A disc-shaped pyrotechnic gas generator includes a housing with a plurality of diffusion holes. A pyrotechnic substance is arranged in the housing. A filter is arranged in the housing. A containment member is arranged in the housing between the pyrotechnic substance and the filter. A drainage member is arranged in the housing between the pyrotechnic substance and the containment member. The filter is to provide support to a supported portion of the containment member at a start of operation of the gas generator.