How an Air Bag Safety System Works

Automotive air bags are made of a stretchable membrane which inflates during a collision to provide cushioning to the head and torso and to prevent injury. The technical term for the air bag safety system is air supplemental inflatable restraint, (SIR) cushion restraint system, or supplementary restraint system (SRS). John W. Hetrick, retired from the navy, invented the air bag system in 1951. 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.

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 seatbelt replacement. In 1971 Ford introduced an experimental air bag system and became the first company to do so. 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 was replaced with the supplemental restraint system or SRS. It was introduced in the S-Class Mercedes-Benz in 1980. The seatbelts 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. The center of the steering wheel contains the airbag inflator module, which contains the nylon airbag and inflator unit. In case of an accident, an electrical signal is sent to the system which releases gas through a hole located behind the airbag inflator, which immediately fills the bag. The electric signal is passed through the coil assembly located on the steering column beneath the inflator 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.

Air Bag in Steering Column

The rest of the airbag, airbag inflator module and electric coil assembly on the passenger side are the same as that 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. The driver's side and passenger side airbags cannot prevent rollover crashes, side impact and rear impact. Later, side impact air bags or the side curtain airbags were introduced to counter this problem. These air bags are located near the exterior side of the seat backs or interior side molding to protect the body. 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. (NOTE: If your air bag light is on or flashing the air bag safety system will not work in the event of an accident).

Air bag technology has advanced greatly since its inception. Airbag triggering algorithms 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.

Air Bag Deployment

Air Bag System Information

Even in the case of power failure or cut-off, the diagnostic and sending module is capable of providing electricity to all the airbag systems. This module is checked every time the automobile is turned on. In case of failure, a ABS warning light will flash or stay on constantly asking for immediate attention. Special care must be taken when disconnecting the anti-theft system and the battery so as not to effect the functioning of the airbag module. The car must be turned off completely with the wheel in a straight position. The battery must be carefully disconnected from negative terminal, then followed by the positive terminal. 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 a fixed stationary object at the speed of 8-14 m/hr. They automatically deflate at a temperature of 300-400 degree Fahrenheit, incase of fire. The efficiency of the system increases when it is used along with a seatbelt 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 ten cm at all times to avoid an adverse effect to the passenger incase of an accident.

How Does it Work / Air Bags

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