GAS GENERATOR FOR AIR BAG

The present invention provides a gas generator for an air bag capable of easily adjusting a volume ratio of two combustion chambers while reducing the gas generator in size. A diameter of an inner cylinder 15 disposed in a housing 11 is increased and reduced depending upon its vertical position. Thus, the volume ratio of the first combustion chamber 20 and the second combustion chamber 25 can be changed without changing the height of the housing 11 itself.