Chevrolet 2002 Impala Owner's Manual page 34

The driver's side impact air bag is designed to inflate in
moderate to severe side crashes involving the driver's
door. The side impact air bag will inflate if the crash
severity is above the system's designed "threshold
level." The threshold level can vary with specific
vehicle design. The driver's side impact air bag is not
designed to inflate in frontal or near
rollovers 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. For
frontal air bags, inflation is determined by the angle of
the impact and how quickly the vehicle slows down in
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frontal and near frontal impacts. For the side impact air
bag, inflation is determined by the location and severity
of the impact.
What makes an air bag inflate?
In an impact of sufficient severity, the air bag sensing
system detects that the vehicle is in a crash. For both
frontal and side impact air bags, the sensing system
triggers a release of gas from the inflator, which inflates
the air bag. The inflator, air bag and related hardware
are all part of the air bag modules inside the steering
wheel, instrument panel and the side of the driver's
seatback closest to the door.
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How does an air bag 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. The air bag supplements the protection
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frontal impacts,
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 the frontal air
bags would not help you in many types of collisions,
including rollovers, rear impacts, and many side
impacts, primarily because an occupant's motion is not
toward the air bag. The side impact air bag would not
help you in many types of collisions, including frontal
or near frontal collisions, rollovers, and rear impacts,
primarily because the occupant's motion is not toward
that 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
collisions for the driver's and right front passenger's
frontal air bags, and only in moderate to severe side
collisions for the driver's side impact air bag.
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frontal