Why Airbags May Not Always Deploy

It has become a common concern by many consumers when their airbags don’t deploy when they’re involved in a minor fender bender however, the force of the impact may not have been sufficient enough to cause airbag deployment. Flooded with information from the Takata airbags cases, consumers have been consumed with the idea of faulty airbags. Defective Takata airbags have been linked to serious injury and death, but mainly because they actually deployed, at times sending sharp pieces of metal into vehicle occupants. I don’t know about you, but I wouldn’t want my airbag to deploy if this is the case.

So why don’t airbags always go off in a collision?  One simple answer, airbags sensors measure deceleration. The vehicles speed and the amount of damage are not indicators that cause deployment of airbags.

Airbags may also deploy when there is no visible damage. NHTSA states, “Occasionally, air bags can deploy due to the vehicle’s undercarriage violently striking a low object protruding above the roadway surface. Despite the lack of visible front-end damage, high deceleration forces may occur in this type of crash, resulting in the deployment of the air bag.”

The key word for airbag deployment is Deceleration.

  1. When a car hits something, it starts to decelerate (lose speed) very rapidly.
  2. An accelerometer (electronic chip that measures acceleration or force) detects the change of speed.
  3. If the deceleration is great enough, the accelerometer triggers the airbag circuit. Normal braking doesn’t generate enough force to do this.
  4. The airbag circuit passes an electric current through a heating element (a bit like one of the wires in a toaster).
  5. The heating element ignites a chemical explosive. Older airbags used sodium azide as their explosive; newer ones use different chemicals.
  6. As the explosive burns, it generates a massive amount of harmless gas (typically either nitrogen or argon) that floods into a nylon bag packed behind the steering wheel.
  7. As the bag expands, it blows the plastic cover off the steering wheel and inflates in front of the driver. The bag is coated with a chalky substance such as talcum powder to help it unwrap smoothly.
  8. The driver (moving forward because of the impact) pushes against the bag. This makes the bag deflate as the gas it contains escapes through small holes around its edges. By the time the car stops, the bag should have completely deflated.

There has been a large effort in reducing the instances of airbag deployment. Why you may ask? Airbags may save your life in a head on crash, but they can just as easily injure or even kill you.

NHTSA states, “Serious or even fatal injuries can occur when someone is very close to, or in direct contact with an air bag module when the air bag deploys.”

The force of an airbag can hurt anyone who is too close to it. “Researchers have determined that the risk zone for driver airbags is the first 2 to 3 inches (5 to 8 cm) of inflation. So, placing yourself 10 inches (25 cm) from your driver airbag gives you a clear margin of safety. Measure this distance from the center of the steering wheel to your breastbone. If you currently sit less than 10 inches away, you can adjust your driving position” (Brain).

Frontal airbags, typically, only work in front-end collisions because they require an abrupt change of speed by deceleration. Many cars are also equipped with “side impact” airbags for side impact collisions. Seatbelts are the effective device used to help in side swipes and crashes, rear-end and secondary impacts. So if your airbag doesn’t deploy in an accident, it may be to protect your safety as the forces of the impact may not have been strong enough to trigger airbag deployment. For more information, follow these links below for more in depth analysis.

Brain, Marshall. “How Airbags Work.” How Stuff Works.   http://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/airbag2.htm

Woodford, Chris. “Airbags” Explain That Stuff. 24 Aug. 2016. www.explainthatstuff.com/airbag  .

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