How do airbags work? – The Hindu

Testing. Testing. The auto mechanics are hard at work making sure the air-filled balloon-looking pillow-like bags work and deploy properly in this sleek and brand new car. Look at the dashboard and see how firmly the system is incorporated. But wait a minute, how does it know when to pop out and how can we make sure it doesn’t harm us? Turn on your thought wheels.

Safely, safety

Airbags have one aim – to protect those inside the car. It is a restraint system which acts to intercept. When a vehicle is met with a sudden impact, the people inside the car tend to move in a direction opposite to that of the forces of collision. This means there is high risk of critical injuries to occur. With airbags, the movement opposite to the forces is restricted and thus, the people inside the car remain relatively safe with lesser injuries. A seatbelt, also a restraint system, works with airbags to protect those inside the car.

Crash protector chemistry

Car companies want to offer best protection with the airbags they provide in their cars. To ensure this, the airbag mechanism goes through a series of simulations and tests for different types of impact conditions. Afterall, crashes aren’t all a single type. For this the bag is prepped thoroughly.

Airbags have one aim – to protect those inside the car. 
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Getty Images/iStockphoto

Airbags are made of strong nylon fabric which does not allow the gas with which it is filled to leak out. It is not normal air around us that’s inside the bag. There is a special chemistry for it. The key chemical involved is Sodium Azide (NaN3). Once the bag is made, they are kept folded at places in the car’s dash.

Chemical Reaction

2 NaN₂ > 2 Na + 3 N₂

Here you go, way too fast

As crashes happen suddenly, airbags cannot waste even a millisecond. Once the sensors in the bag detect a crash, the airbag has to be inflated quickly before damage is done. Once the crash is sensed, electric signals are sent to the igniter which triggers an exothermic reaction where sodium azide decomposes to produce nitrogen gas. This gas fills up the airbag. Since the sensors need a bit of time to do the detecting, the inflation has to be even quicker. Typically the full process takes about 25 to 30 milliseconds (0.025 to 0.03 seconds!)

Then, in about 50 milliseconds, the person inside the car comes into contact with the airbag. The airbag intervenes and absorbs the sudden forward movement reducing injuries and damage.

Things to note

Airbags are fantastic when there is space between the bag and the person. If the person is too close to where the airbag is, the immediate inflation can cause grave harm. This is why it’s advised that airbags should be used in conjunction with seatbelts. Make sure your seat is a good distance away. For children, care must be taken to ensure that they are properly buckled up for the ride. It is advised that children should be placed in the back seat. Ensure that the airbags aren’t defective.