Abstract: In an air bag (1) in an air bag unit, which is inflated by high pressure gas from an inflator operated in an emergency, it is formed by woven cloth in hollow weave where edges (2) are at least partially provided in single weave (6). Because the air bag (1) is formed from woven cloth in hollow weave, the air bag (1) can be manufactured simply by forming the base cloth (5) of the air bag (1) in advance, which is made of woven cloth in hollow weave with its part in single weave (6) and by cutting the base cloth (5) at the single weave portion (6). In this case, because a part of the desired portion can be woven in single weave and the other can be woven mechanically in hollow weave in cylindrical shape, the above base cloth (5) can be easily manufactured. This eliminates such procedures as the procedure to cut a plurality of air bag components into the desired shape and the procedure to sew up the cut components by aligning the edges.

Abstract: The air bag 3 according to this invention is furnished with exhaust outlet 6 to discharge internal gas, and the material 8 with and heat-shrinking property is provided, which blocks at least a part of the exhaust outlet 6 in normal case and shrinks to such direction as to increase the passage area of said exhaust outlet when reaction gas is introduced from the inflator 2. Therefore, the passage area of the exhaust outlet 6 is relatively narrowed down by the heat-shrinking material 8 in normal case. For this reason, it is rapidly expanded by reaction gas from the inflator 2. Thereafter, the material 8 is shrinked by the heat of reaction gas and the passage area of exhaust outlet 6 is increased. Thus, more reaction gas flows out of air bag 3, and this alleviates the impact when the air bag 3 receives the person in the vehicle.