Abstract: This invention relates to an air bag inflation gas generator used to inflate air bags such as air bags for impact safety devices, life jackets, rafts, and escape chutes, and aims to simplify its structure extensively as compared with prior art and to make the device compact easily. Combustion gas produced when gas generating agents are burnt passes through a gas filter which is disposed inside the outer wall of a combustion chamber and flows from gas outlets of the outer wall directly into an air bag. When the combustion gas passes through the gas filter, residues contained in the combustion gas is collected by the gas filter to purify the combustion gas. And, the combustion gas produced when gas generating agents are burnt is changed its passage by gas passage changing means, and the residues contained in the combustion gas are collected between a partition member and the gas passage changing means before the combustion gas enters the gas filter.