PURPOSE: To prevent an automobile from sinking, and facilitate the escape from a window by providing a gas generating means and a gas igniting means in a housing having a gas discharge port in a gas generator, and providing a working means to work the igniting means when the automobile falls into the water.

CONSTITUTION: A gas generator is provided with a gas generating means, i.e., a gas generating agent 15 in a housing 20. A diffuser shell 1 of a housing 20 is provided with a plurality of openings 9 (gas discharge port) to communicate a filter chamber 19 with an air bag. When an automobile falls into the water, wheels are idled and the torque signal of a detecting means 21 in a working means becomes zero, and a control means 24 makes a judgement that the automobile falls into the water, and outputs the working signal to a slive 10 of an igniting means 30. This constitution ignites an enhancer 6 to break the wall of a canistor container through an opening 7, and ignites the gas generating agent 15 inside. The gas passes through the openings 9 and flows into the air bag.