How do Car Airbags work?

A look at how car airbags work to save you in the event of a crash...

How do Car Airbags work?

Mass and velocity work well together until you have to stop suddenly or you hit something. When you hit something in your car the kinetic energy has to go somewhere.

Some of the energy will be absorbed with the disintegration of the car however that energy can still be a huge risk to occupants of a vehicle because people or objects inside a vehicle will keep moving forward until they themselves hit something to stop moving.

Seatbelts are used to stop our bodies moving forward in a crash but it doesn’t stop your head, arms or legs from continuing to move and unfortunately the nearest thing to stop you if you haven’t got an airbag is a steering wheel, seat, dash or window.

The chance of serious injury in a high speed crash is high if you rely on the seatbelt alone that is why manufacturers designed the supplementary restraint system, known as the airbag, to aid the seatbelt functionality.

Without the seatbelt being used the airbag wouldn’t offer too much protection in an accident, seat beats and airbags work in conjunction with each another for the best results.

All cars sold in Australia must comply by the Australian Design Rules which advise all cars must meet safety standards in regards to the types of body injuries that can occur if involved in an accident.

Manufacturers fit cars with airbags to meet these necessities, it is not a legal requirement to fit airbags, however the most sensible option, otherwise they would have to meet safety regulations by other means.

Most new cars will have at least 4 airbags and anywhere up to 10 or even more.

You will be happy to know airbags are expected to last the life of the vehicle so there shouldn’t be any need to replace airbags unless you have an accident.

But if you ever see your airbag light staying on you should get it looked at by a qualified mechanic.

Airbags are designed to only deploy when necessary and they rely on sensors around your vehicle that determine what speed you hit something and at what angle the hit comes from.

These sensors will decide if the airbag needs to be deployed.

If you are hit from behind the airbag won’t deploy as your head will move backwards and the headrest is there to stop your head flying backwards and hopefully prevent your neck from breaking.

Even if you find that your vehicle has gone into a side roll the airbags probably won’t deploy, unless have specific side airbags for side impacts.

It may be a good idea to find out how many sensors are on any vehicle you are looking to purchase as the more sensors the more likelihood you will be covered sufficiently in an accident.

Now that we know there are sensors around the vehicle to identify when the car is hit, what extent the impact is and in what direction the impact is coming from.

Now how is it that the airbag explodes because once an impact has been detected the airbag will inflate at over 300 km/h.

The sensor will send a message to the Electronic Control Unit (ECU) within 0.003 milliseconds.

The ECU will then process the extent of the collision and if it thinks it needs to deploy the airbag a message will be sent to the airbag inflators within 0.015 milliseconds.

The ignitor of the inflators is activated, this causes a chemical reaction that creates a gas which inflates the airbag within 0.020 milliseconds.

By the time the driver has started moving forward the airbag is inflated and ready to cushion the impact within 0.040 milliseconds.

Energy will be absorbed through the car being crushed, the seatbelt and the airbag will also absorb energy from the driver within 0.060 milliseconds.

This timeframe is for the driver, if you are a passenger your energy will be absorbed within 0.120 milliseconds.

All this happens in less time that it takes you to blink.

There are various types of airbags fitted to vehicles nowadays and you can have numerous types in your car.

Here are some of the different types available:

  • Side Curtain airbags – deploy from roof sill to protect from side impact and roll overs, remain inflated
  • Side torso airbags – deploy from the side of the seat and stay inflated for side impact
  • Front airbags – deploy from steering wheel and dash, will deflate after impact
  • Side airbags – deploy on side impacts and sometimes in rollovers
  • Foot bags – deploy in the foot well to reduce foot and leg injury
  • Seatbelt airbags – deploy across the body and shoulder from the seatbelt
  • Knee airbags – protect knees from dash and steering column in frontal collisions
  • Rear curtain – protects the rear passengers head deploys across back window
  • Rear centre – deploys from centre of back seat so passengers don’t hit one another
  • Seat cushions – deploy behind your knees to lift your legs up
  • Front centre – deploys between front passenger and driver to avoid hitting one another
  • Hood – deploys at base of windscreen to protect pedestrians
  • Motorcycle – to assist in motorcycle collisions (effectiveness is inconclusive)

There are regulations when it comes to airbags and children.

If you allow your child to sit in the front sit of a vehicle, depending on the size of the child, you may need to switch the front airbag off or best practise is don’t allow them to sit in the front.

Due to front airbags being designed for adults you could be putting your child at higher risk of serious injury or death if you allow them to sit in the front seat and have an accident.

Check your owner’s manual to see what airbags you have in your vehicle and where they are located so you know where you will be protected in an accident

Another good tip is to make sure you don’t place items in front of an airbag these items will be flung towards you if there is an accident.

Also make sure you do not sit to close to an airbag.

If you are the driver you should sit with your back and shoulders against the seat with your wrist resting on top of the steering wheel, this will mean that when driving you will have slightly bent arms and will not be sitting to close to the steering wheel and airbag.

Ideally front passengers shouldn’t be sitting close to the passenger airbag.

Seatbelts and airbags working together have increased are chances of surviving vehicle collisions and the technology increases with numerous varieties being introduced in new vehicles.

This ingenious design that reacts in milliseconds when needed has proven to be a necessary safety device and a great life saver.

Thanks to AutoGuru for this handy info on car airbags.

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