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Seats & Safety Belts
When is an air bag expected to inflate?
The air bag is designed to inflate in
moderate to severe frontal or near-frontal
crashes. The air bag will only inflate if
the velocity of the impact is above the
designed threshold level. When impacting
straight into a wall that does not move or
deform, the threshold level for most
GM vehicles is between 9 and
14
mph
(14
and 23 km/h). However, this velocity
threshold depends on the vehicle design
and may be several miles-per-hour faster
or slower. In addition, this threshold
velocity will be considerably higher if the
vehicle strikes an object such as a parked
car which will move and deform on
impact. The air bag is also not designed to
inflate in rollovers, side impacts, or rear
impacts where the inflation would provide
no occupant protection benefit.
In any particular crash, the determination
of whether the air bag should have
inflated cannot be based solely on the
level of damage on the vehicle(s).
Inflation is determined by the angle of the
impact and the vehicle's deceleration, of
which vehicle damage is only one
indication. Repair cost is not a good
indicator of whether an air bag should
have deployed.
What makes an air
bag
inflate?
In a frontal or near-frontal impact of
sufficient severity, sensors strategical
located on the vehicle detect that the
vehicle is suddenly stopping as a result of
a crash. These sensors complete an
electrical circuit, triggering a chemical
reaction of the sodium azide sealed in the
inflator. The reaction produces nitrogen
gas, which inflates a cloth bag. The
inflator, cloth bag, and related hardware
are all part of the air bag inflator modules
packed inside the steering wheel and in
the instrument panel in front of the
passenger.
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