How do Airbags Work?

If you ever get caught up in a car accident, airbags and seatbelts are your best shot at survival. But what exactly are airbags, and how do they work?

What are airbags?

These inflatable cushions are installed in the steering wheel, dashboard, doors, and often the seats of a vehicle. Most vehicles also have curtain airbags (i.e. overhead), seatbelt airbags, knee airbags, and centre airbags. Airbags are designed to inflate and deflate quickly in the event of a collision. Typically, a force of around 12mph is required to inflate an airbag.

How do airbags work?

So, how exactly do airbags work? Let’s walk you through a simple scenario and break down the science behind these vehicle-occupant restraint systems.

Picture this: you’re setting off on your morning commute. As you’re driving along, a car to your left pulls out in front of you without warning. Although you slow your car and brake as you should, there’s not enough time to prevent an accident. How does your car respond?

When your car collides with another object, it decelerates rapidly. Your car will use an accelerometer to measure the force or acceleration of your car and detect any sudden changes caused by a collision.

If the rate with which your car has decelerated is dramatic enough, your car's accelerometer will trigger the airbag circuit in your vehicle. Once this circuit is activated, a heating element is activated, which sets a chemical explosive into action. This chemical explosive will flood your airbag with large amounts of gas, inflating your airbag and shooting it outwards to protect you from the impact.

How do airbags inflate so quickly?

The solid propellant (or gas) which is ignited inside your airbag burns at a rapid pace. After all, this is a literal explosive! While explosives in your steering wheel may sound like a recipe for disaster, airbags need to inflate in the blink of an eye to save your life. What better way to do this than with an instantaneous chemical reaction?

The most common explosive used in airbags is sodium azide. While this chemical is toxic (even in small amounts), it poses minimal risk to your safety in this application. Airbag manufacturers will mix sodium azide with other compounds to encourage the reaction, whilst simultaneously reducing your risk of exposure.

The sheer power of these chemicals is what causes your average airbag to inflate within just 10-20 milliseconds of impact. Pretty incredible, right? Most European airbags will take no longer than 25 milliseconds to inflate, meaning they need to expand as quickly as 160mph.

Industry advice states that your car's airbags are designed to last a lifetime. So, unless you’ve noticed any faults yourself, they won’t need checking when you next go for a service.

Where does the plastic from the dashboard go when the airbags pop out?

In most cases, the airbag covers in your vehicle are designed to split open and push to the side when your airbag inflates. It’s unusual for this plastic to completely break away and cause you any harm. In most cases, the plastic covers around your airbag remain attached to the vehicle; they just open and split rapidly to allow the airbag to inflate.

How effective are airbags?

Research shows that airbags are one of the most effective ways to minimise injury or fatality in an accident. For example, one study found that between 1985 and 1993, airbags reduced the number of fatalities in frontal collisions by as much as 24%!

The bottom line

While airbags are not a substitute for seatbelts, they’re one of the most effective safety measures in your vehicle, and the science behind them makes them even more impressive.

If you have any concerns about your vehicle safety, contact your local Tyre Pros centre for more advice.