Abstract: An operation control system to be used with a vehicular air bag system having an air bag and an inflator comprises an inhibit circuit for preventing a useless expansion of the air bag and inhibiting the later operation of the air bag by detecting that a touch sensor already has its contacts closed, when the ignition switch acting as a main switch for an igniting circuit of the squib of the inflator is switched from OFF to ON, if the contacts of the touch sensor are closed when the ignition switch is OFF. Also comprised is an acceleration type collision sensor acting as a second collision sensor for causing the air bag to be expanded if an acceleration detected exceeds a predetermined level, even if in the inhibited state by the inhibit circuit.