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The Miracle of Airbags & How They Work

When it comes to safety in your car and on the road, airbags and how they work is one of the most miraculous inventions ever made. It’s one of the most revolutionary safety inventions since Volvo released the seatbelt patent and made them accessible to everyone, and they save countless lives on a daily basis. They really don’t get the recognition they deserve.

What’s even more amazing in this situation than what the airbag does, however, is how it actually does it and how airbags actually work both inside and out, as well as why it is so vital to the preservation of life and making us all safer on the road.

To really develop that understanding to where it needs to be, that means we need to look at a few different things.

Crash Physics

First of all, let’s look at what a car crash really is and what’s going on during it. When we’re driving, we’re moving a huge mass of metal (and people/objects). To do that, we generate horsepower from our engines to propel us forwards, at any speed, or velocity, that we like.

When we force that speeding mass to stop, that energy transfers elsewhere, and causes a huge amount of damage in the process depending on what it takes to stop the car (faster + heavier means harder). That can come in one of two ways, too, and it matters much more than you might think.

Example 1

One of the more obvious examples of a crash is a car hitting into something stationary. Whether that is a tree, a wall, or even another car, the car is being forced to stop immediately. All of the energy you had wrecks the car and whatever you hit, and you’re susceptible to the same thing even inside the car. You have the exact same force happening to your body too. The quicker the reaction takes place, the more rapid the energy transfer is and the more damage is done too. That’s what crumple zones are for, but they don’t replace airbags.

Example 2

In the same sense, exactly the same reaction can happen even if you’re going much slower, too. Not many people realise this, but the physics of a crash actually means you can make a crash much worse even when you’re not going as fast as you could. For example, making your car too heavy is an easy way to do it, as it’s much harder to stop that much momentum. Another is to hit something moving towards you, like another car doing the same speed. Two cars similar in weight hitting head on both at 40mph is very similar to hitting a wall or a tree at 80mph because there’s momentum from both ways creating a combined force.

It’s dangerous stuff, even when you don’t know it. That’s why airbags and understanding how they work is so essential.

Why We Need Airbags

This just opens up more doors as to why we need these magical bags of safety. When all of this is going on and your car is being forced to stop, for whatever reason, your body is doing the same. You are inside a box going through this massive energy transfer and have your own going on too, from your own mass and speed. The difference, however, is that you’re stopped by your seatbelt, if you’re wearing one, as well as the rest of the car too.

Whether your seatbelt stops you or not, you can still do a huge amount of damage to yourself when you’re crashing a car. That’s because your head and your neck aren’t supported or fixed into place, and when you stop, you move these forwards with a huge force. The result at best is a heavy and violent jerk forwards, and then an even worse one going back. That’s what whiplash is. You’re putting a huge strain on your back, neck and your head. If you’re not wearing the belt, you instead hurtle forwards and collide with your steering wheel, dashboard or even a passenger seat in the back. Either way, it’s a huge impact on your whole body.

Airbags and how they are designed to work is a way to stop both of these things from happening. The bag deploys to keep your head in place and take the force out of your personal reaction as it absorbs the blow.

How does the Airbag work?

Let’s move on to what we’re really here for. How does the airbag work in all this? It’s actually a double-edged sword in this respect, as there are two parts to the airbag reaction. They both have an amazing effect to help keep you safe and save your life.

Step 1- The Explosion and Inflation

Firstly, the bag has to fill up. That’s how this whole system works, and it’s the only thing that is going to absorb all of this force by supporting your head in the reaction. To do that, it’s actually down to a chemical reaction.

The bag collecting air would take much too long in a car crash, so instead, we use an explosion. A chemical explosive inside the airbag, and when you break unnaturally hard as is with a collision, the explosion releases a huge burst of gas which causes the bag to inflate dramatically and rapidly. This is what essentially hits you in the face and keeps you in pace with a soft blow.

Step 2 – The Deflation on impact

After the bag has done its job and saved you from flying forwards, it also has to make sure it doesn’t knock you back with even more force than there was before. A reaction that fast could push you even harder than you already could be after all. To do that, the bag has to minimise the blow as soon as you collide with it.

To do that, the bag actually deflates almost as fast as it inflates. As soon as you impact with the bag, the gasses are pushed out of holes all around the bag to make it deflate. That prevents a bouncing effect of the bag and means your neck doesn’t slam you back into the seat. It’s really an extremely intelligent invention.


Ultimately, that’s the whole thing. How airbags work is mostly through a crash, an explosion inflating the bag, and your impact causing it to deflate, preventing you from moving more than you should. It’s one of many incredible safety features that your car has to protect you, like crumple zones to take away the force by prolonging the reaction and even the seatbelts stopping you hitting the dash. They all work together to protect you and your loved ones even without you knowing they exist.

Cars are always going to be dangerous when crashes occur. There’s no such thing as a safe crash when you’re on the road, and all of the physics and precautions in the world can’t keep you safe. The best lifesaver you have when you’re driving is your concentration and ability to follow the rules of the road. It’s essential that you drive as well as you can, and do so safely, calmly, and minimise the risks you take. If things do ever go wrong, the equipment is there to help. Check the health of these safety features when you can and however you can, especially if you buy a new car, and always make sure your car is safe.

Stay safe, and happy driving!

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