Gas generator for air bag

A gas generator for an air bag which includes a housing having gas outlet ports, gas generation means disposed inside of the housing and ignition means for igniting the gas generation means, such that a gas generated in the gas generation means by an impact occurring when a car crashes is introduced into the air bag for protecting a driver or passengers of the car from the impact occurring during the collision, characterized in that

• said ignition means includes a mechanical sensor (5) having piercing pins, a cap piece (6) disposed in close proximity to said mechanical sensor and having hole portions (9) disposed to deviate from the central axis thereof in the radial direction, percussion caps (7) put in said hole portions of said cap piece and forced to ignite by said piercing pins, and a transfer charge container (8) disposed in close proximity said cap piece for containing a transfer charge, and
• said mechanical sensor includes at least TWO positioning pins (15) provided on the end surface facing said cap piece and disposed to deviate from the central axis thereof in the radial direction, while said cap piece includes hole portions (17) for putting in said positioning pins.