Airbags - Part II

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Vince recently needed to fix the window of our car so it wouldn't go up. This involved removing the airbag assembly which made us wonder how they actually work. It is all very interesting. Firstly sensors detect a collision and an electric signal is sent to a canister in the airbag assembly which contains sodium azide and a small amount of igniter compound. The compound ignites and the heat causes decomposition of the sodium azide. This generates nitrogen gas which is what actually fills the air bag. 130 grams (a handful) of sodium azide produces 67 litres of nitrogen gas. This whole process takes only 30 milliseconds (0.03 of a second). How amazing is that? Something else I didn't really appreciate about airbag deployment – it can cause breathing problems, particularly in those with pre-existing respiratory conditions such as asthma. The effect is likely to be most severe if a person cannot get out of the vehicle within a short space of time. Children sitting in the front seat can be at risk of injury simply from the force of an airbag deploying. I also read in our car's manual that dash mats, phone and drink holders, etc, can interfere with the efficient operation of airbags both those situated in the front and any situated in the side panels. Broken bones, skin abrasions and other minor injuries can also occur when airbags go off. Although a great safety device, they are not really big fluffy pillows. Have you ever been involved in an accident and had an airbag go off? I showed one side of the airbag assembly in my previous post. This shows the other side. The canister containing the sodium azide is on the lower left. You can see the dotted lines which would break to allow the bag to escape.