An air bag system (10) is provided for use in a motor vehicle. The air bag system includes at least one air bag module (100). A multiple level gas generation source is coupled to the air bag module for generating a selected gas generation level applied to the air bag module. An electronic control unit (200) controls the operation of multiple level gas generation source. At least one temperature sensor (206) is coupled to the electronic control unit for sensing ambient temperature. At least one seat belt sensor (208) is coupled to the electronic control unit for sensing seat belt usage. An acceleration sensor (204) is coupled to the electronic control unit for sensing deceleration during a crash. The electronic control unit is responsive to a combination of sensed inputs from the temperature sensor, the seat belt sensor and the acceleration sensor for determining both an optimum gas generation level and inflation sequence times for controlling the multiple level gas generation source.