Why is Sodium azide is used in car air bags?

Answer 1

Sodium azide is an explosive. If it is struck hard enough, has a sufficiently high voltage applied across it, or if it is heated to a certain high temperature, then it will explode.

The reaction for the explosive decomposition of sodium azide is:

2NaN3 ---> 2Na + 3N2.

As you can see, a small amount of sodium azide solid decomposes very fast to give a lot of nitrogen gas. The nitrogen gas is what fills up the car's airbag. A sensor, in the form of an accelerometer, tells one of a car's computers whether the car hit something hard enough to cause the driver to hit his head on the steering wheel or even the windshield (if the driver is not wearing his seatbelt). If the computer determines that the impact was hard enough, then a fuse is lit which leads to a plug of compressed sodium azide powder which then explodes.

As you can imagine, the fuse is very short. Because the sodium azide explodes, the airbag is filled almost instantly.

For an airbag to potentially save your life or keep you from receiving a serious head injury, it is very important for everyone to wear their seat belts.