PURPOSE: To make the wall of a filter by dividing a coolant filter chamber by means of a retainer to make gas pass through each chamber in order, arranging coolant and a filter in the gas passage of each chamber and effectively utilizing the broad area of the coolant and filter.

CONSTITUTION: A coolant and filter chamber 19 is formed by surrounding a combustion chamber 5 which is filled with gas generating agent, and the interior is divided into a plurality of chambers 15, 16, and 17 by a retainer 10. In the first chamber 5, an exhaust nozzle 8 forms an inlet port, and a gap 18 provided axially separated from the exhaust nozzle 8 constitutes an outlet. The gap 18 which is an outlet is the inlet of the second chamber 16, and gas enters the third chamber 17 in the same way, and an exhaust nozzle 9 becomes an outlet for the gas. To the gap of the gas which flows in such manner as mentioned above, coolant 13 is arranged in the chambers 15 and 16, and a filter 12 is arranged in the chamber 17, and the gas is cooled in the broad area of this coolant 13. In the next step, the gas cleaned by the filter 12 in the chamber 17 is supplied to an air bag from the flowout port 9.