GMC 1995 Safari Owner's Manual page 33

When should an air bag inflate?
The air bag
is
designed to inflate in moderate to severe frontal or
near-frontal crashes. The air bag will inflate only if the impact speea 1s
above the system's designed "threshold level." If your vehicle goes straight
into a wall that doesn't move or deform, the threshold level is about 11 to 16
mph (1 8 to 26 km/h). The threshold level can vary, however, with specific
vehicle design,
so
that it
can
be somewhat above or below this range. If your
vehicle strikes something that will move or deform, such as a parked car, the
threshold level will be higher. The air bag is not designed to inflate in
rollovers, side impacts, or rear impacts, because inflation would not help the
occupant.
In any particular crash, no one can say whether an
air bag should have
inflated simply because of the damage to
a
vehicle or because of what the
repair costs were. Inflation is determined by the angle of the impact and the
vehicle's deceleration. Vehicle damage is only one indication of this.
What makes an air bag inflate?
In a frontal impact
of
sufficient severity, the air bag sensing system detects
that the vehicle is suddenly stopping as a result of a crash. The sensing
system triggers a chemical reaction of the sodium azide sealed in the
inflator. The reaction produces nitrogen gas, which inflates the air bag. The
inflator, air bag, and related hardware are all part of the air bag module
packed inside the steering wheel.
How does an air bag restrain?
In moderate to severe frontal or near-frontal collisions, even belted
occupants can contact the steering wheel. The air bag supplements the
protection provided by safety belts. Air bags distribute the force of the
impact more evenly over the occupant's upper body, stopping the occupant
more gradually. But air bags would not help you in many types of collisions,
including rollovers and rear and side impacts, primarily because an
occupant's motion is not toward the air bag. Air bags should never be
regarded as anything more than a supplement to safety belts, and then only
in moderate to severe frontal or near-frontal collisions.
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