Mechanics

Air Bag Safety

This article explains automotive air bag safety systems front and side air bags.

If an air bag warning light is illuminated while driving the air bag safety system has been disabled and will not activate in the event of an accident. The center of the steering wheel contains the airbag inflation module, which contains the nylon airbag and inflation unit. In case of an accident, an electrical signal is sent to the system that releases gas through a hole located behind the airbag inflation, which immediately fills the bag. The electric signal is passed through the coil assembly located on the steering column beneath the inflation module.

This electric signal is converted to heat, which burns the copper oxide, which converts to nitrogen gas and fills the air bag. In the passenger side, the area above the glove compartment holds the air bag and SRS is displayed on the compartment, which means supplemental restraint system. The rest of the airbag, airbag inflation module and electric coil assembly on the passenger side are the same as in the steering wheel unit. The airbag is contained within a trim cover, which has a molded seam through which the airbag inflates open after the seam splits.

Side impact air bags or the side curtain airbags were introduced to aid in the safety. These air bags are located near the exterior side of the seat backs or interior side molding for protection. Some side air bags can be located in the roof, back seat outboard edge or the door. The door pillar near the bottom holds the impact sensors, which sends out electric signals to inflate the side impact air bag. Airbag triggering systems have become more advanced and sophisticated, helping to prevent injury and death.

Conditions like proximity and position of the passenger, severity of crash, and belt usage are being considered prior to SRS action. To reduce the force and impact of airbags, multi-stage inflators have been developed to help control the force of deployment based on whether the crash was severe or moderate. According to a research, air bags when accompanied with seat belts, reduces the number of deaths due to automobile accidents by about eight percent.

Drivers Side Air Bag
Drivers Side Air Bag

Air bags were first commercially available in the 1970s. At that time drivers were not required to wear seatbelts and air bags were considered a seat belt replacement. In 1971 Ford introduced an experimental air bag system. General Motors followed in 1973 introducing a new system, which had two-stage deployment, in their Chevrolet cars. At that time these systems were known as air cushion restraint system. One significant difference between the early airbags and those used today is that the passenger side airbag was placed at the bottom of the dashboard, protecting the knees, instead of above the glove compartment.

The initial air bag system was enhanced and replaced with the supplemental restraint system or SRS which was introduced in the S-Class Mercedes-Benz in 1980. The seat belts were also made to tighten at the time of an accident to maximize the benefit of the airbag. The 1987 Porsche was the first to introduce the passenger side airbag.

Air Bag in Steering Column
Air Bag in Steering ColumnAutomotive air bags are made of a stretchable membrane which inflates during a collision to provide cushioning to the head and torso to prevent injury. The technical term for the air bag safety system is supplemental inflatable restraint or (SIR), cushion restraint system, or supplementary restraint system (SRS). Air bag technology currently used in cars is derived from a system used in aircraft in the 1940s. The original air bags were bladders, filled with heated or compressed air. That system was quite large in comparison with modern air bag technology, but works on the same principle.

Air Bag Deployment
Air Bag Deployment

Air Bag System Information

Even in the case of power failure the diagnostic and sending module is capable of providing electricity to all the airbag systems. This module is checked every time the automobile is started. In case of failure, an SRS warning light will flash or stay on constantly asking for immediate attention.

The car must be turned off completely with the wheel in a straight position. The battery must be carefully disconnected from negative terminal and then followed by the positive terminal and a manufacturer specific amount of time must pass to allow for capacitor discharge. When working with the airbag module, do not face it towards the body or any surface in case of accidental inflation to avoid injury.

Airbags inflate when the car hits an object at the speeds above 8 to 14 MPH. They automatically deflate at a temperature of 300-400 degree Fahrenheit, in case of fire. The efficiency of the system increases when it is used along with a seat belt because the body is properly positioned. It is always recommended to wear the seat belt when the vehicle is in motion. The passenger in the front seat should be away from the air bag about 10 cm at all times to avoid any adverse effects to the passenger in the event of an accident.

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-11-19)