Also known as Supplementary Restraint Systems (SRS), airbags are designed to stop the human body coming into contact with potentially damaging hard points in a car, in the event of a collision.
As the name suggests, they’re designed to be used in addition to a seat belt – not instead of one. An airbag has to slow a car occupant’s forward motion as evenly as possible in a fraction of a second.
It’s reckoned that the fitment of an airbag reduces the chance of death or serious injury by around a third
Three areas help to accomplish this feat; the first is a bag made of a thin nylon, which is folded into the steering wheel, dashboard, seat or door.
Triggering this is a sensor that tells the bag to inflate, if a collision takes place over 10-15mph. The airbag's inflation system reacts sodium azide with potassium nitrate to produce nitrogen gas, a hot blast of which inflates the airbag. All of this happens in just 1/25 of a second, with the bag bursting from its storage area at around 200mph.
However, because the bag is full of tiny holes, it deflates almost immediately, so it’s all over before you can even register what’s happened. Despite the speed of it all, it’s reckoned that the fitment of an airbag reduces the chance of death or serious injury by around a third – so it’s not just a load of hot air.