Gas generator, with safety device, for an air bag

The gas generator has a cylindrical housing, the front ends of which are closed by closure covers. A cylindrical outer section of the housing consists of high-grade steel; whereas the closure covers are made of aluminum, which has a thermal conductivity which is greater many times greater than that of the high-grade steel. In at least one of the closure covers, there is inserted a self-ignition device, which is provided with an ignitable material, that automatically ignites when reaching a minimum temperature. This minimum temperature clearly lies below the self-ignition temperature of the pressure gas-generating charge contained within the gas generator. The poor thermal conductivity in the cylindrical section of the housing prevents heat transport or transfer from outside via the housing to the pressure gas-generating charge; whereas the good thermal conductivity of the closure covers allows the quick heat transport to the self-ignition device.