Air Bag Deployment – What to Expect

Air bag safety restraint systems are currently being used in many new model vehicles. These systems have been designed to deliver an extremely high level of deployment reliability. To verify their system performance, vehicle manufacturers have collected statistical data which confirms that deployment failures as well as unnecessary or unexplained deployments are extremely unlikely.

An air bag should deploy only after specific deployment criteria are experienced by the vehicle. Although the requirements may vary by vehicle manufacturer, all current systems are designed to deploy during frontal impacts (see Figure 1) or similar sudden motion changes at specific test velocities and predetermined angles of impact.

Most published air bag deployment speeds were determined using a rigid stationary barrier; however, when two vehicles are involved in an impact, the actual closing speed will be approximately twice the stationary barrier equivalent speed.

When an air bag equipped vehicle is involved in an impact (depending on manufacturer requirements), one or more impact sensors must close and signal the system to deploy the air bag. Sodium Azide in the gas generator is then ignited to produce a measured amount of nitrogen gas which inflates the air bag. A small amount of Sodium Hydroxide powder and other Sodium compounds also results from this controlled reaction.

The inside of the air bag is coated with a type of talcum powder or corn starch which keeps the bag material from sticking to itself during storage. The majority of this powder, along with the small amount of Sodium compounds, is ejected from the airbag vent holes during the inflation and deflation process. This generally covers the entire passenger compartment of the vehicle with a fine layer of light colored dust. Cracks and corners of the vehicle interior in the area directly below and behind the steering wheel, are also likely to be covered with this dust.

If a repair facility or insurance adjuster encounters a vehicle with a deployed air bag, and the driver of the vehicle and/or the accident report indicate that a deployment did not occur during the collision, a thorough investigation should be conducted to determine the actual cause of the deployment. This should be done before the vehicle is repaired in order to assure that this safety system will function properly when the vehicle is returned to the owner.

If the cause of the unexplained air bag deployment cannot be determined at the local level, the automotive manufacturer and other government safety organizations may wish to participate in the investigation. Their participation may help determine the cause for any unexplained deployments.

During any vehicle repair, the manufacturer's safety recommendations should be followed explicitly.

The information provided in this bulletin is for educational purposes only. Although every effort has been made to ensure the accuracy of the information contained in this bulletin, Tech-Cor assumes no responsibility or liability for any repairs performed using information from any publication issued by Tech-Cor.

Any person performing repairs must determine whether any suggested or recommended procedures or repairs are suitable or appropriate for the particular vehicle being repaired. The repairer remains solely responsible for such determination, as well as for the proper completion of the repairs.

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