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Car Airbag: What is it and How it Works?

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SRS airbag works hand-in-hand with seat belts to cushion passengers during a car accident.


Not all explosions are bad.

Some explosions, may just save your life.

Car airbag (a.k.a SRS airbag) is your first line of defence in a car crash.

During a frontal collision, a controlled explosion will set off a chemical reaction that inflates the airbags.

As the passenger is being fling forward, the airbag meets the passenger midway to cushion the impact.

It has to team up with car seat belts to hold you back from hitting the interior of your car.

So now you have something that holds you back, and something that cushions just in case!

According to National Highway Traffic Safety Administration (NHTSA), frontal airbags alone have saved over 44,500 lives from 1987 to 2015.

That’s more than enough people to fill a stadium!

In fact, SRS airbags are capable of reducing driver fatalities by up to 52 percent in a frontal collision according to the Insurance Institute for Highway Safety (IIHS).

Now I don’t know about you, but I’m eager to know how this extraordinary invention saves life.

Feel free to skip ahead to whichever section that you are interested in.

What is a car airbag and why do we need it?

The legend, the hero! John W. Hetrick is the American engineer who invented airbag. Image courtesy of UpClosed.

John W. Hetrick is the brilliant man who laid the foundations for the airbags that we use today.

It all began with a normal Sunday afternoon trip to Pennsylvania countryside. Hetrick was travelling with his wife and seven-year old daughter.

“We were watching for deer bounding across the road.”

“Suddenly, there was a large rock in our path.”

“I remember slamming on the brakes and steering the car to the right. We crashed into the bush but managed to avoid hitting the tree and wooden fence, which would be way worst.”

“As I applied the brakes, both my wife and I threw our hands up to keep our daughter from hitting the dashboard. During the ride home, I couldn’t stop thinking about the accident.”

“I asked myself: ‘Why couldn’t some object come out to stop you from striking the inside of the car?‘”

He went to work and finally got awarded the patent in 1953.

Fast forward 20 years, this patent eventually led to Oldsmobile Toronado, the first commercial passenger car equipped with an airbag system.

Oldsmobile Toronado is General Motor's first experimental production run of car airbags.
Oldsmobile Toronado 1974 is General Motor’s first experimental production run of car airbags. Image courtesy of Ryan Hildebrand.

An airbag, in layman’s terms, is a balloon-like system made from stretchable fabric which is tightly packed in the dashboard, door, roof, or seat of your car.

During any major collision, the airbags will erupt and be filled with gas to a volume of 30 litres or 70 litres. This provides a cushioning effect to the passengers so that they do not collide with the windshield or dashboard.

And guess what? All these steps happens within 0.04 sec.

That means if you can pop them consecutively, you can deploy 25 airbags in just 1 second!

The airbag will immediately deflate through vents in its lining so that they do not hinder with the driver’s vision.

How exactly does car airbags work?

This is How an Airbag Works & Takata Recall jam-packed into a short 4 minutes video by speedkar99. Great stuff.

An SRS airbag system consists of the airbag, inflation module and crash sensor.

It all begins with the crash sensor.

During our normal drive, a crash sensor is constantly monitoring the deceleration of our car.

During a crash/collision, the crash sensors detects the sudden change of speed and immediately reports to our car’s Electronic Controller Unit (ECU).

Judging from the collision type, angle and severity of the impact, the ECU’s crash algorithm determines if the event meets the criteria to deploy airbags.

Normal braking or a minor crash into a pole would not trigger the airbags.

But, if the crashing force is stronger than that of hitting a brick wall at 20 km/h, the ECU will classify it as a major collision.

If it is a major collision, the ECU will send electric current to start the igniter.

The igniter will spark a rapid chemical reaction between sodium azide and potassium nitrate. This reaction produces hot nitrogen gas to inflate the airbag.

Finally, the inflated airbag will burst out through the module into the car space and cushion the passengers.

As mentioned above, this whole procedure will be completed in just 0.04 second.

Airbags must inflate rapidly to reduce the risk of the occupant hitting the vehicle’s interior.

Types of Airbags

Different types of airbags are mounted throughout the car to protect occupants in different crash scenarios, including side impact and rollover events.

When we talk about airbags, most people will only think of frontal airbags. Truth is, there are many other kinds too and they are equally important.

Modern vehicles may contain multiple airbag modules. Some even up to nine airbags, it’s almost enough to be a balloon castle!

There are four main types of airbags: frontal airbags, side-impact airbags, knee airbags and pedestrian airbag.

Frontal Airbags

You can see two examples of Toyota’s Land Cruiser frontal airbags here: driver’s head airbag and front passenger’s head airbag.

As the name suggests, frontal airbag activates on frontal collision. It helps to stop the passenger from hitting the dashboard or windshield.

Here are a few different types of frontal airbags:

  • Driver’s head airbag
  • Front passenger’s head airbag
  • Dual-stage front airbags (It inflates to match the size of the person)
  • Rear passenger’s head airbag

Side-Impact Airbags (SABs)

The picture showcase two examples of Toyota Land Cruiser’s side-impact airbags: torso airbags (left) and curtain airbags (right).

Side-impact airbags are designed to help protect your head and/or chest in the event of a serious crash involving the side of your vehicle.

There are four main types of SABs:

  1. Torso airbag
  2. Head airbag
  3. Curtain airbag.
  4. Front-center airbag (Found between the seats. It is a new innovation by General Motors to prevent front passengers from colliding with each other.)

Knee Airbags

Just like Toyota Land Cruiser’s knee airbags, most knee airbags are located below frontal airbags.

This is a feature that keeps people in their seated position during crash. Usually found below the steering column and glove box.

  1. Driver’s knee airbag
  2. Front passenger’s knee airbag

Pedestrian Airbags

2015 Land Rover Discovery Sport features a pedestrian airbag. Credits to TestDriven for making this short but informative video.

Pedestrian airbag is mounted to the exterior of vehicles to protect walking pedestrian. It covers the hard part of windshield and the A-pillar, because that is where the pedestrian usually strikes.

Inflatable Safety Belts

Ford’s inflatable safety belts just made safety belt… safer!

In 2011, Ford introduced an inflatable seat belt airbag to reduce rear-seat injuries. It spreads the crash force across the passenger’s torso and chest hence reducing the risk of injury.

The deployment of airbag also tightens the seat belt itself, reducing forward movement.

How much does an car airbag cost in Malaysia?

SRS airbags are very expensive. They can cost as much as RM 10,000.
SRS airbags are very expensive. They can cost as much as RM 10,000.

Great question. This is a RM 10,000 question. Literally.

A driver’s side airbag can cost between RM 5,000 to RM 10,000 ++ depending on the car model.

Yes, they’re definitely not cheap!

Airbag alone costs RM 3,000 to RM 4,000.

Wire harness, inflation module and impact sensor will set you back another RM 2,000 to RM 3,000.

Finally, there is the labour charge as well.

Sure, you may find some aftermarket SRS airbag from half cut shops for around RM 2,000. But, it is recommended that you stay away from these.

I’m a big fan of D-I-Y because it saves money. But when it comes to airbag, never do it yourself.

Here’s why.

  • Airbags contains explosive charges. Without the technical know-how, they are ridiculously easy to set off when working on it.
  • Salvaged airbags may not be functional anymore. They are generally not well taken care of. Some may have suffered flood damaged and will not work when needed. There is also no standard method to test the functionality of a salvaged airbags.
  • Car maker, model and year are often not enough to ensure a match of airbag. SRS system components are changed within model years by many manufacturers.
  • Lastly, you would need to get someone to reset your ECU deployment code to certify that the job has been done properly. I don’t think any reputable workshop would want to stake their reputation to earn a quick buck!

This could be a matter of life or death and we should do everything in our power to make sure that the system runs perfectly when it matters. I strongly recommend that you get your airbags replaced at an authorized dealer’s place.

Airbag can cause harm. How NOT to use airbag?

As with all things in the world, there are always the good and the bad.

SRS airbag is not always unicorns and rainbows too.

Instead of serving its very purpose to protect, airbags can cause injuries too.

The deployment of an airbag is an explosion which inflates very aggressively. So aggressive that the airbag expands at 320 km/hr to meet and cushion the passenger before he/she hits the dashboard.

Yikes! That’s worst than being punched in the face.

If your sitting posture is not proper, the deployment of SRS airbag can lead to chest injuries, concussions and whiplash.

Have a look at this video to see it for yourself.

I know it’s very comfortable, but you should never rest your legs on the dashboard.

Good new is… We can minimize the risks if we know about it.

Here’s how.

1. Make sure you are seated at least 25 cm away from the steering wheel.

Timing is key here.

Airbags are designed to meet the passenger midway. Too early or too late can result in too much force or too little cushion from the airbag.

Leaving 25cm ~ 40cm of space between you and the steering wheel when seated is a good idea.

2. Always wear a seat belt.

Airbags are called SRS airbags for a reason. In fact, SRS is short for Supplemental Restraint System.

As the name suggests, it is only a S-U-P-P-L-E-M-E-N-T-A-R-Y restraint system.

During a crash, seat belts need to hold you in proper position to meet the incoming frontal airbag.

This helps to cut down on potential airbag injuries for both drivers and passengers.

3. Children under 9 years old or 145 cm should ride in a children safety seat (a.k.a booster seats).

Children below 9 years old should sit on a booster seat at the rear passenger seat.
Children below 9 years old should sit on a booster seat at the rear passenger seat. Image courtesy of BruceBlaus.

All car’s seat belts are designed for adult use and they should (ideally) rests on our chest.

Depending on a children’s height, it can rest on their tummy.

This is a big no-no.

She could suffer stomach or liver damage during a car crash.

If the seat belt rest against her neck, the children may move the seat belt to under her arms so it’s more comfortable.

During an accident, this can crack her ribs and damage her internal organs.

It’s wise to invest in a children safety seat to keep your loved ones safe.

4. Keep your kids (12 and under) at rear center seat.

If your children have already outgrown booster seat, you should seat them at the rear center seat.

Children will feel uncomfortable sitting in seats designed for adult use.

Children being children, they will move around a lot and some may even scoot up onto the dashboard (if they sit in front).

This is extremely dangerous.

According to U.S. National Transport Safety Board, the safest place for children to sit is in the center of the backseat, buckled up with a lap-and-shoulder seat belt.

So next time, maybe you can try bribing them with a lollipop to have them sit there.

Your child can graduate into a normal seat belt only when she can keep her head resting against the back of the seat, her knees naturally bend over the edge of the car seat and her feet stay flat on the car floor.

5. Check for airbag manufacturer’s recall

In some cases, there may be defects from the car manufacturer too.

Take the infamous Takata airbag incident for example. Takata’s defective airbags can explode under high heat and humidity, sending metal shrapnel towards the driver.

It’s literally a ticking time bomb!

NHTSA reported at least 23 deaths and 300 injuries caused by this defective airbag.

This has led to mass airbags recall. In the US alone, 19 car manufacturers are recalling 37 million cars and 49.5 million airbags between 2002 and 2015.

If you’re worried, check out Paul Tan’s Airbag-related recalls in Malaysia to find out if your car is affected.

If your car is one of the affected model, please get it changed immediately.

Obviously, these are outliers event. But if possible, check your car manufacturer’s website periodically for any car recalls just to be on the safe side. 

The Future of SRS Airbags

As you can see, SRS airbag is great but leave many to be desired still. Engineers are always asking “How do we make it better?”

Easy. Prevention is always better than cure.

As of 2018, we are seeing a shift towards “active safety” instead of “passive safety”.

  • Active safety helps to prevent accidents. For example, anti-lock braking system and lane departure warnings.
  • Passive safety helps to reduce injuries during an accident. For example, airbags and car crumple zones.

But that doesn’t mean the end of airbag era, it only mean better airbags. Because car crash is always a possibility and we want to be ready for the “What if-“.

Looking ahead, automobile manufacturer will start to install forward-looking sensors that works in harmony with airbags. In the near future, we may start to see airbags to deploy just before a collision and with lesser force.

That will surely help to minimize airbag injuries even more.

What’s more? General Motors also have their own take on advanced airbag.

The airbag uses a unique vent that pushes out excess nitrogen gas quickly upon impact.

This makes the airbag softer which features a gentler impact. The airbag debuted on 2013 Chevrolet Cruze on the driver side only.

The sky is the limit.

We don’t know how airbag will end up in 20 – 30 years, but we do know that it will just keep getting better.

Perhaps we will see a day where car accident fatality is a thing of the past. Wouldn’t that be great?

Comment down below if you had your car airbags replaced before. Sharing your experience can really help the community!

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