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. 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 impact
of
sufficient severity, sensors
strategically 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 the cloth bag. The inflator, cloth bag, and related
hardware are all part
of
the air bag inflator 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
provide protection 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 belt protection in moderate to
severe frontal and near-frontal collisions.
What will
you
see after an air bag inflation?
After the air bag has inflated, it will then quickly
deflate. This occurs
so
quickly that some people may
not
even realize that the air bag inflated. The air bag will
not
impede the driver’s vision or ability to steer the
vehicle, nor will it hinder the occupants from exiting the
vehicle. There will be small amounts
of
smoke coming
from vents in the deflated air bag. Some components
of
the air bag module in the steering wheel hub may be hot
for a short time, but the portion
of
the bag that comes
into contact with you will
not
be hot to the touch. The
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