airbags what happens when one goes off?

safety first

airbags what happens when one goes off?

Ever wondered what would happen if the airbag in your car went off? Jonathan Crouch reports

"We all know that the airbag is a great safety feature in our cars and, used in conjunction with a seat belt, can often save serious injury. What most of us don't know is what it's like when one goes off.

GEM Motoring Assist member Matt Day recently wrote to the organisation to describe his first experience of an airbag doing its job admirably when he and his wife were involved in a crash that was not his fault.

"We were thankful for the extremely fast deployment of the airbags," said Matt. "They seem to have deflated again before I realised they had inflated. What's more the seatbelts did their job and we didn't get thrown forward."

Matt explained that when the airbags inflated his car filled with smoke from the mini explosion, which was necessary to deploy them. "I could sense the car filling rapidly with smoke and my initial reaction was to get out. I screamed at my wife to get out too."

He said the crash made him think that there should be more information as to what exactly happens when an airbag comes into use. "In a situation where you might be best off not moving at all, especially if you are injured, your first reaction is to try and get out of the car," he said.

So how do airbags actually work? Extremely quickly is the short answer. When one goes off, there's an explosion no louder than the sound of a paper bag being burst which propels the nylon bag towards your face. Since it's not completely gas tight, it will automatically deflate again within a split second so as not to impair your vision or hamper your escape from the car.

It doesn't hurt - volunteers describe it like being hit with a pillow - and since an airbag distributes the force of impact so evenly, it's unlikely to shatter your glasses. Even if you're smoking a pipe, there's little danger, it's likely that the force of deceleration will have flung it from your mouth.

Typically, an airbag will be fully inflated within 30 milliseconds (0.03 secs) after the point of impact. To ensure that it doesn't go off accidentally, or trigger in minor impacts, a threshold deceleration has to be reached before the sensors activate inflation. In Europe, this can be anything from 12-20mph.

There are few recorded instances of airbags going off accidentally. They're manufactured to military equipment standards, hermetically sealed and designed to last at least ten years. Providing that the triggering mechanism is working properly, malfunctions are almost unheard of.

Manufacturers do warn however, against exposing them to excessive heat (such as would be generated by a blowtorch or welding equipment), ill-advised tampering by DIY enthusiasts (don't) and excessive bashing of the module in the centre of the steering wheel.

Most parents now know that they must ensure that rear-facing child safety seats are not placed in the front, should the car be fitted with a passenger side airbag. Simulations with full-sized American airbags have shown that children can be harmed in this way.