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Air bags with properly worn seatbelts, are more effective than safety belts alone for reducing overall risk of fatalities and injuries. Since 1984, when automatic crash protection for passenger cars was mandated, the number of cars equipped with air bags has increased dramatically.

Air bags or supplemental restraint systems are just that, a protection system that supplements the safety belt.


The basic subsystems of the air bag system are:

•the crash sensors and associated wiring harness

•the air bag modules with inflators

•the diagnostic module with readiness indicator


Air bag systems rely on crash detection systems containing sensors to trigger deployment. The sensors are located in different parts of the vehicle.

Crush zone sensors are located at the front of the vehicle. They activate the air bag when they are struck by the crushed structure of the vehicle.

Non-crash zone sensors are located in the passenger compartment area. These sensors activate the air bag when they detect a significant change in velocity which occurs during an accident.


Sensors should respond to a fixed barrier impact speed of approximately 18 km/h or higher. There is a 'may deploy' speed range from 13 km/h to 18 km/h. This reflects the variability in, for example, crash sensor and vehicle structural performance. Below an impact speed of 13 km/h, no airbag deployment is desired.

To date, there have been some complaints of late or premature airbag deployment.

The airbag is inflated within about 30 milliseconds by a pyrotechnic gas generator located in the steering wheel hub or passenger side dashboard. The airbag prevents the head and upper body from striking the steering wheel or lower dash.

Even in a crash of moderate severity, relative minor injuries can occur, such as abrasion from contact with the deploying airbag (airbag fabric abrasion on the skin).


There are not skin burning chemicals involved. "Smoke" is actually visible particulate matter or powder which is produced in all airbag deployments. Corn starch or talcum powder, along with sodium compounds, is used as a lubricant.

Safety belts must be worn and worn properly. Airbags are not designed to deploy in every crash, (i.e. side, rear, rollover, or mild frontal impacts). Also, as an airbag inflates and deflates very quickly, the safety belt is needed for protection during any subsequent impact. Safety belts offer risk reduction against the possibility a properly deployed airbag could cause injury to an occupant who is in close proximity to where the airbag is stored.


Rear facing infant seats must never be used in the front seat with a passenger side airbag. The top of the carrier is very near to the airbag as it starts to inflate.

Misconceptions and complaints about airbag performance and function have been addressed by providing a better understanding of airbag operations.

The combination of safety belts and airbags can provide the greatest overall reduction the risk of injury or death in traffic crashes.

The information contained in this web site is intended for marketing purposes only. It is not all-inclusive, and does not fully describe the many and varied services that the company provides, nor does it completely describe the education, training, skills, or expertise of our staff.


Walters Forensic Engineering | 277 Wellington Street West, Suite 800 | Toronto, ON M5V 3H2
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