What Makes An Airbag Inflate; How Does An Airbag Restrain - GMC 2008 Envoy Denali Owner's Manual

In any particular crash, no one can say whether an
airbag should have inflated simply because of the
damage to a vehicle or because of what the repair
costs were. For frontal airbags, inflation is determined
by what the vehicle hits, the angle of the impact,
and how quickly the vehicle slows down. For roof-rail
airbags, deployment is determined by the location
and severity of the side impact. In a rollover event,
roof-rail airbag deployment is determined by the
direction of the roll.
What Makes an Airbag Inflate?
In a deployment event, the sensing system sends
an electrical signal triggering a release of gas from
the inflator. Gas from the inflator fills the airbag causing
the bag to break out of the cover and deploy. The
inflator, the airbag, and related hardware are all part
of the airbag module.
Frontal airbag modules are located inside the steering
wheel and instrument panel. For vehicles with roof-rail
airbags, there are airbag modules in the ceiling of the
vehicle, near the side windows that have occupant
seating positions.

How Does an Airbag Restrain?

In moderate to severe frontal or near frontal collisions,
even belted occupants can contact the steering wheel
or the instrument panel. In moderate to severe side
collisions, even belted occupants can contact the inside
of the vehicle.
Airbags supplement the protection provided by safety
belts. Frontal airbags distribute the force of the impact
more evenly over the occupant's upper body, stopping
the occupant more gradually. Roof-rail airbags distribute
the force of the impact more evenly over the occupant's
upper body.
Rollover capable roof-rail airbags are designed to
help contain the head and chest of occupants in the
outboard seating positions in the first and second rows.
The rollover capable roof-rail airbags are designed to
help reduce the risk of full or partial ejection in rollover
events, although no system can prevent all such
ejections.
But airbags would not help in many types of collisions,
primarily because the occupant's motion is not toward
those airbags. See When Should an Airbag Inflate? on
page 1-58 for more information.
Airbags should never be regarded as anything more
than a supplement to safety belts.
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