Answer:Yes.
Most air bags are triggered electrically by a signal from the vehicle's
crash sensors and/or ABS control module. It's about as failsafe a system
as engineers can design. The sensitivity threshold of the crash sensing
system is set high enough so that normal bumps and jolts cannot cause
the bag to go off. In fact, the air bag usually doesn't go off unless
the force of the impact is equivalent to hitting a sold barrier at a
speed of 15 to 18 mph or higher (which explains why the bag may not
go off in a minor fender bender). But there are some circumstances where
the bag may be inadvertently or accidentally deployed.
One is an accidental electrical short. The wires that
run to the air bag are routed down the steering column and under the
dash along with dozens of other wires. If you're doing electrical
work under the dash and short out a hot wire to one of the wires in
the air bag circuit, it could result in a rather loud and unexpected
boom from the air bag. The bag deploys with explosive force, which
might injure you if you're in the way. The counterforce generated
by the bag is designed to protect occupants who are wearing seat belts
and facing forward in an upright position, not someone who is working
on the car or just sitting behind the wheel.
To prevent this from happening, always disconnect
one of the battery cables before doing any electrical work or working
on any part of the air bag system (including the steering wheel).
Emergency rescue personnel such as paramedics and police officers
are trained how to deactivate air bags. This may be necessary if a
person is trapped in a vehicle with an air bag and the air bag has
not deployed. The last thing they want is the air bag exploding as
they're trying to extract an injured person from the wreckage. Disconnecting
the battery doesn't necessarily deactivate the air bag because the
control module often contains an internal battery that keeps the system
armed for up to several minutes. This is actually a safety feature
that allows the air bag to work in case the battery cables are severed
during a crash.
Many air bag equipped vehicles have a special orange
or yellow connector at the base of the steering column that can be
disconnected to temporarily disable the air bag. The ignition must
be off when this connector is disconnected or reconnected. The connector
may have a tag labeled SRS (Supplemental Restraint System) connector
or SIR (Supplemental Inflation Restraint) connector.
Another situation where an accidental air bag deployment
may occur is when plowing snow with a truck or sport utility vehicle
fitted with a snow blade. Due to the severe jolts or bumps that may
occur when ramming into things with a blade, the air bag system should
be deactivated prior to plowing by removing the system fuse or unplugging
the air bag connector(s) per the vehicle manufacturer's instructions.
The same situation may occur when off-roading in a four-wheel drive
vehicle. Again, deactivating the air bag will prevent jolts and bumps
from setting it off.
A final word about air bags: they are designed to
deploy and protect in frontal collisions only (except for Volvo's
new side impact system which also protects during side collisions).
The air bag is not supposed to go off in a side collision, if the
vehicle is rear ended or rolls over (but they sometimes do). |
Answer:
Yes
and no. You can now purchase an "aftermarket" air bag to fit
certain late model vehicles that did not come factory-equipped with
an air bag, but you can't install it yourself. It has to be professionally
installed by a trained technician. Air bags do save lives, and are well
worth the extra cost. According to the Insurance Institute for Highway
Safety (IIHS) and the National Highway Transportation Safety Administration
(NHTSA), air bags account for a 25 to 29% reduction in moderate or severe
injuries compared to passive seat belts alone. IIHS researchers have
also found 24% fewer deaths than in cars equipped with air bags than
those equipped with seat belts alone. Unfortunately, air bags were not
offered as an option or standard equipment until 1989. GM offered air
bags as an expensive option briefly back in the 1970s, but a low key
marketing effort and a lackluster reception by the public limited the
number sold to only about 10,000. So air bags bombed and were forgotten
until the federal government's decision to require passive restraint
systems (automatic seat belts or air bags) in 1990 touched off a boom
in air bags that brought the bags back.
Crash tests show that factory 3-point seat belts do
a fairly good job of protecting the driver's body in a frontal collision,
but may not always keep the driver's head from hitting the steering
wheel (which can result in severe injury or even death). The SRS-40
air bag is designed to provide additional protection to the factory
seat belts by adding an extra margin of safety. When the bag inflates
during a crash, it "fills the gap" between the driver and
steering wheel. The inflated bag provides the cushion necessary to
absorb the force of the impact and prevent the driver's head or face
from striking the steering wheel.
The SRS-40 bag uses similar technology the larger
original equipment air bags that Breed supplies to Jaguar and the
'95 Jeep Cherokee. It features a "mechanical" impact sensor,
which is the simplest, most reliable type of triggering mechanism.
Unlike most original equipment air bag systems that rely on a complex
web of crash sensors, safing sensors, wiring and an electronic control
module, the mechanical impact sensor is virtually fail-safe. The crash
sensor, which is self-contained within the steering wheel air bag
module, consists of a steel ball within a tube. When a frontal impact
of sufficient force occurs, the ball is dislodged and slides down
the tube, releasing a firing pin that ignites the inflator. The bag
deploys in 30 to 55 milliseconds (less time than it takes to blink
your eyes), which is just as fast as an original equipment air bag.
Before the bag will deploy, the crash sensor has to experience an
impact force of about 7 G's (seven times the force of gravity). For
most vehicles, this would be the equivalent of hitting a solid barrier
at 12 to 15 mph, or hitting another vehicle at a speed of about 25
mph. The actual crash speed at which the bag will deploy depends on
so many different variables (angle of impact, the relative mass of
the vehicle or object struck, the stiffness of the body and chassis,
etc.), that it's impossible to give an exact speed. The only thing
that can be said with certainty is that the air bag will deploy when
it is needed.
One of the advantages of having an air bag with a
purely mechanical crash sensor is that it eliminates the need for
wiring and expensive electronics. This allows the crash sensor to
be packaged with the inflator in the air bag module, which greatly
simplifies replacement and installation. It also means the system
will function independent of the vehicle's electrical system. Because
the SRS-40 air bag with its purely mechanical crash sensor can be
packaged as a self-contained unit, it can be easily installed on just
about any vehicle -- provided there's a steering wheel available for
the application designed to accept the SRS-40 air bag module -- and
that the required crash testing has been done to make sure the crash
sensor has the correct level of sensitivity for the vehicle.
Though
it's relatively simple to replace a steering wheel and bolt on one
with an air bag, the SRS-40 isn't a "one-size-fits-all"
air bag. The bag has to "fit" the application, which means
different inflators and crash sensors are required for different vehicle
applications. An air bag with a crash sensor that's set for a lightweight
Toyota, for example, may not deploy at the right speed if used in
a heavier vehicle such as a full-sized Ford. So Breed currently has
five different inflator assemblies that make up its SRS-40 air bag
system. To install the air bag, a technician selects the appropriate
module for the application, removes the stock steering wheel and installs
a new steering wheel that contains the air bag. The entire job start
to finish takes less than 30 minutes. |
