How does the safety belt pretensioner and air bag supplemental
restraint system work?
The safety belt pretensioner and air
bag SRS are designed to activate
when the vehicle sustains
longitudinal deceleration sufficient
to cause the sensors to close an
electrical circuit that initiates
pretensioner activation and air bag
inflation.
The fact that the pretensioners and
air bags did not activate in a
collision does not mean that
something is wrong with the system. Rather, it means the forces were
not of the type sufficient to cause activation. Front air bags and
pretensioners are designed to activate in frontal and near-frontal
collisions, not rollover, side-impact, or rear-impacts unless the collision
causes sufficient longitudinal deceleration.
The air bags inflate and deflate
rapidly upon activation. After air bag
deployment, it is normal to notice a
smoke-like, powdery residue or
smell the burnt propellant. This may
consist of cornstarch, talcum
powder (to lubricate the bag) or
sodium compounds (e.g., baking
soda) that result from the
combustion process that inflates the
air bag. Small amounts of sodium
hydroxide may be present which
may irritate the skin and eyes, but
none of the residue is toxic.
While the system is designed to help
reduce serious injuries, contact with
a deploying air bag may also cause abrasions, swelling or temporary
hearing loss. Because air bags must inflate rapidly and with considerable
force, there is the risk of death or serious injuries such as fractures,
facial and eye injuries or internal injuries, particularly to occupants who
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