TP 2436 Road Safety Leaflet
CL 9601 (E)
Revised October 1996
Air bags are safety devices of proven value that supplement the
protection provided by seat belts. Transport Canada has been receiving
complaints from the public about injuries caused by air bags that inflate
in low-speed collisions and about incidents in which air bags did not
open when it seemed they should have. This leaflet answers commonly asked
questions about frontal air bags, and it provides advice on how to prevent
being injured by a deploying air bag.
How Do Air Bags Work?
Air bags are connected to sensors that detect sudden deceleration.
When activated, the sensor sends an electrical signal that ignites a
chemical propellant, and when ignited, this propellent produces nitrogen
gas, which inflates the air bag. This process occurs very quickly—in less
than one-twentieth of a second—faster than the blink of an eye. Most air
bags have internal tether straps that shape the fabric and limit the
movement of the bag. Vents in the rear allow the bag to deflate slowly
to cushion the head as it moves forward into the deploying air bag.
Sensors deploy air bags only when deceleration exceeds a minimum
threshold. If the change in speed due to an impact is lower than the
threshold, the air bag will not inflate. In low- to moderate-speed
collisions, the seat belt alone is usually sufficient to prevent serious
injury. In high-speed crashes, the seat belt may not be able to prevent
the driver’s head from striking the steering wheel or the passenger’s
head from hitting the dashboard. Frontal air bags protect the head and
upper body in frontal crashes and are not designed to open in rear-end
collisions, side impacts, or rollovers. Air bags may deploy in
undercarriage impacts and angled collisions, including side impacts,
where there is sufficient longitudinal deceleration.
Smoke, some of which is caused by residual combustion products, may
be present in the vehicle following the inflation of an air bag. In
addition to creating smoke, deployment also releases powder that is in
the air bag folds to prevent them from sticking together.
Why Do Air Bags Sometimes Cause Injuries?
In order to protect the head and upper body in high-impact crashes,
air bags must inflate so quickly, and with such force, that they can
cause injuries. While most of these injuries are minor, consisting only
of bruises and abrasions, some are more serious, such as broken arms. In
extreme cases, such as when the head or chest is against the module when
it opens, fatal injuries can result.
People who sit close to the steering wheel are at higher risk of being
injured by a deploying air bag than those who sit further away. Small
children are also very vulnerable. Children aged 12 and under should
always be seated in the back of the vehicle and should be properly
restrained. Never allow a child to sit or stand near the dashboard.
In addition, never install a rearward-facing infant restraint system
in a seat equipped with an air bag—if it deploys, the infant restraint
system will be propelled into the back of the seat.
What Can We Expect of Air Bag Systems in the Future?
In Canada, it is not mandatory for air bags to be installed in vehicles;
however, when they are, they must meet specific safety requirements.
Whenever possible, Transport Canada sets standards of performance and
does not stipulate that particular hardware be used by manufacturers.
In the case of air bags, the Regulations specify vehicle test conditions
and injury criteria for the effective protection of occupants.
In order to reduce the incidence of air-bag-induced injury, motor
vehicle manufacturers are developing “smart” air bags. Already some
possess two thresholds of activation, one that is appropriate for a
belted occupant and another, lower threshold, for an unbelted person.
The next generation of air bag systems will probably have proximity
sensors that gauge how close an occupant is to the air bag module and
will be equipped with warning systems that signal when someone is too
close—for instance, when a driver has fallen asleep and is slumped over
the steering wheel. Some vehicles already have a manual cut-off switch
that disables the passenger- side air bag when an infant restraint system
is installed; in the future, automatic systems may prevent the air bag
from deploying.
What Can I Do in the Meantime?
You can maximize the protection offered by current occupant restraint
systems and reduce the risk of being injured by an air bag by taking the
following precautions.
General Guidelines:
- Always wear your seat belt.
- Adjust the seat belt properly. Place the lap belt as low as
possible over the hips—not over the abdomen. Ensure the shoulder belt
lies on the chest and over the shoulder. Do not leave any slack in the
belt.
- Adjust the vehicle’s front seats as far to the rear as possible to
give the air bags as much room as possible in which to inflate.
Guidelines for Children:
- Children aged 12 and under should be seated in the back of the vehicle
- Make sure the infant restraint system, the child restraint system, or
the booster cushion is properly suited to the child’s height and weight.
- Always ensure that the restraint system is properly secured by the seat
belt to the vehicle.
- Secure the child properly in the restraint system.
- Never install a rearward-facing infant restraint system in a seat
equipped with an air bag.
- Never place the shoulder strap of a seat belt behind the child’s back
or under the arm.
If you have any questions about air bags, or any other issue related to
motor vehicle safety, please telephone Transport Canada’s Road Safety Information
Centre at:
- 1-800-333-0371 toll free in Canada, or
- (613) 998-8616 in the Ottawa area.
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