a metal bridge initiator , with or without a spark gap feature , for firing an air bag inflator is deposited on a thin plastic film substrate . the bridge can be tuned by adjusting the width and thickness of the substrate . the bridge is of compact size enabling an increase in the strength of the inflator in the initiator area thereof . if there is an initiator structural failure , the very small feed through slot into the interior of the inflator will plug up with the products of combustion of the inflator . the intimate contact between the deposited metal bridge and plastic substrate makes the initiator resistant to vibration , bending and damage . the method of manufacturing is simpler than for conventional inflator initiators and is adapted to mass production .