Restraint systems (Airbag modules): Description and operation (page 2 of 2)

Both airbag modules operate in the same way. On receipt of a fire signal from the airbag ECU, the igniter ignites the material in the gas generator. The burning material rapidly produces a large amount of nitrogen gas which passes through the filter screen into the airbag, forcing the airbag to unfold. On the driver airbag module, the unfolding airbag ruptures the cover along the split lines; on the passenger airbag module, the unfolding airbag breaks the deployment door fixings to the module housing and trim panel, and the deployment door lifts off the fascia (but remains tethered to the module housing). Once free of the housing the airbag inflates to its full extent. Vents in the airbag prevent excess pressure bursting the bag and, as soon as the material in the gas generator is exhausted, allows the airbag to instantly deflate.