Can an airbag break your arm?

After the bang

October 2020

It bangs, it dusts, it smokes, it smells burnt. In addition, the shock of the impact that has just been overcome. The side effects of the airbag are similar to a bomb for many accident victims.

The foot on the brake, the hands clasping the steering wheel spasmodically - nevertheless the vehicle races inexorably towards the obstacle. In the few seconds before the crash, you try to arm yourself for the inevitable impact, but the following goes beyond all expectations.

A deafening bang. Smoke and the smell of fire in the interior cause panic. You are dazed and only gradually understand what has happened. That was not a soft cushion in which one is comfortably immersed, as slow-motion recordings often suggest. In reality, the airbag flies towards you with force. And he's gone again, hanging limply from the steering wheel.

Airbags have been an integral part of passive safety in cars for decades. "Only the combination of seat belts / airbags / body and their targeted deformation in the event of a crash ensure the high chances of survival in serious accidents. The airbags installed in many places in the interior distribute the high load on the human body best when decelerating," explains ÖAMTC technician Steffan Guy.

"I don't remember the accident itself, just the noise and smell from the airbag. It smoked so much that I thought a bomb had hit the car. Only a police officer explained to me afterwards how such an airbag works." , says Frieda Glashüttner. Despite decades of experience driving a car, she did not know the exact effects of an airbag opening - and she is not alone in that.

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They just talk about how great airbags are and how many lives they save. But nobody tells you what to expect when an airbag is deployed.

Frieda Glashüttner, Lower Austria

Mystery airbag

What Makes These Nasty Life Saver Side Effects? This can be answered by taking a closer look at the individual components of an airbag system and their function.

Airbags: An important part of the system is clearly the airbag itself. This is usually made of polyamide fabric and folded up compactly. The smoke that arises in the car when it is triggered has a very harmless origin: the fabric of the airbag is coated with a powder that has the purpose of reducing the friction both in the textile itself and on the skin surface of the occupants when it is triggered. It is precisely this powder and a little exhaust gas from the pyrotechnic deployment of the airbag that creates what appears to be "smoke" in the interior of the vehicle.

Propellant: Depending on the size, airbags are inflated using different methods. Smaller airbags are equipped with cold gas generators. These are simple metal cartridges filled with CO2 or nitrogen. There is a primer on this that "opens" the cartridge in the event of a crash. Then the gas flows into the airbag until the cartridge is completely empty. The Austrian company iSi is a leading manufacturer of such cartridges.

With the larger-volume front airbags, however, the compressed gas would not be sufficient for timely inflation, because airbags do not have more than seven milliseconds to deploy. The gas required for the front airbags is generated pyrotechnically, i.e. by an explosion. To trigger this, black powder is ignited in a squib. That then creates the burnt smell.

Crash sensors: These components are inertia switches that interrupt the electrical input signal to the fuel pump in the event of a significant delay. They are mounted as far on the outside of the vehicle body as possible so that they can be triggered from an acceleration of 3 to 5 g without losing much time. The sensors are installed twice for safety.

Control unit: In the seven milliseconds, the control unit of the crash sensor checks which airbag should be triggered, as well as the energy supply to the ignition circuits and defines the severity of the crash on a scale from 0 to 3.

Safing sensor: The task of this sensor is to prevent the airbag from being triggered unintentionally. Under normal driving conditions, it interrupts the ignition lead to the airbag and only closes when the load is around 2 g.

Painful rescue

The 21-year-old Marcel Wintscher has already experienced two accidents with airbags being deployed. He once suffered a slight concussion from the airbag and a bruise in his teeth. The powder thrown up and the smell of the explosion stuck in his mind, too. “When I came to, I panic. I thought the car was starting to burn. "

Hannes Fröhlich from Lower Austria only noticed the pain in his ribs and burned wrists a few hours after his accident.

So one cannot speak of a gentle rescue with airbags. In the event of an accident, the occupants are thrown forward with great force. The belt holds the occupants in place. The airbag has the task of catching individual body parts such as the head. So it has to be inflated very aggressively and at lightning speed. This can cause additional injuries such as bruises.

In addition to the physical impact of the airbag, chemicals released during inflation can also cause irritation to the eyes. Burn injuries can also be caused by the friction during the sudden deployment.

ÖAMTC director Oliver Schmerold also had to experience this painfully in a head-on collision. "I didn't even consciously notice the explosion as an extra noise in the fraction of a second, but when the vehicle was stationary I saw the smoke and the floury powder everywhere. The airbags saved us from serious injuries, the only burns on my forearms were. because the airbag snapped over my uncovered arms. "

I heard a terrible bang, got a blow from the airbag and then it was dark before my eyes.

Marcel Wintscher, Carinthia

An incorrect hand position on the steering wheel can lead to even more serious injuries. "The importance of the correct steering wheel position is often underestimated," explains Roland Frisch, chief instructor of the ÖAMTC driving technology. "When the airbag is triggered, if they are unfavorably on the steering wheel, they can throw their hands forcefully into the driver's face. The safest hand position corresponds to the pointer position three-quarters three on the face of a clock - one hand on the left on the steering wheel, the other on the right at about the same height. This protects the head of the handlebars. "

It is also important that the lap belt is tight. Otherwise the body could be lifted out of the seat and thrown backwards by the airbag. This can also lead to serious injuries.

Torment for the ears

A deploying airbag is no walk in the park for the ears either. The bang of an airbag is an impressive 170 decibels. Anyone who has ever heard a New Year's Eve explode close to their ear can roughly imagine the volume of an airbag.

The term "bang trauma", damage to the inner ear caused by very high, briefly acting sound pressure, only became known since the introduction of the airbag. The noise level is not the main cause, but the sudden increase in pressure in the vehicle due to the explosion. Vehicle manufacturers are trying to counteract this problem by using more, but more compact, airbags. No more bags are inflated than are necessary for occupant safety. Nevertheless, the loud bang cannot be prevented.

I was very happy that I had an airbag. Otherwise it wouldn't have turned out nicely.

Hannes Fröhlich, Lower Austria

Sometimes the possibility is raised that an accident with the shock of an "exploding" airbag could have psychologically stressful after-effects - such as temporary hypersensitivity to popping noises. Of course, this cannot be ruled out entirely.

"Smells, noises and images of the accident scene can keep circling in the mind for some time or trigger connections when similar conditions exist," explains ÖAMTC traffic psychologist Marion Seidenberger. However, there do not seem to be any specific cases of psychological stress that can be attributed solely to the airbag.

Despite everything, the life-saving function of the airbags is beyond question. "Working together, both seat belts and airbags have prevented countless serious physical injuries and saved lives," the expert emphasizes.

© Kurt Pinter