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How do airbags work?

October 19, 2022 by

Airbags are fitted to almost every new car on the planet; we explore why this is, and how they work

Car safety has changed a lot over the years: it was only in 1991, for example, that rear-seat occupants were legally required to wear seatbelts, but today, all new cars coming with a host of safety equipment, and airbags chief among these.

There’s a reason for this, and it’s both easy to understand, and backed up by data: airbags stop your vulnerable body parts impacting with hard surfaces in the event of a collision, inflating to act as a cushion that absorbs energy and reduces the chance of injury or worse. American estimates hold that over 50,000 lives had been saved by airbags as of 2017.

Airbags first appeared on high-end luxury cars in the late 1980s, before becoming commonplace in the 1990s and beyond.

Steering-wheel-mounted driver airbags were first to appear, before front-seat passengers got them as well. Since then, airbags have appeared on almost every interior surface of the car, from curtain airbags that appear from the roof of the car to protect heads in a side-on collision, to airbags for drivers knees, and even seatbelt airbags that can spread collision forces across passengers’ laps and torsos. Even pedestrians have benefitted from airbags, with some cars featuring a ‘bag that emerges from the bonnet to cushion people on foot who are hit by a car.

Example of side airbags fitted to the Volvo V40

How do airbags work?

The physics behind airbags is pretty simple: on-board sensors look out for movements that indicate a vehicle has been involved in a collision, triggering the airbag to fire if a crash is detected.

When this happens, a small explosive device detonates within an airbag module, inflating the bag, which fills with air to protect vehicle occupants.

The technology has developed over the years, with some airbags able to detect the forces involved in a collision, inflating to the correct amount based on this data.

Airbags are also known as ‘supplementary restraint devices’ because they are designed to work in conjunction with seatbelts, which themselves control how your body behaves in a crash. This name is what some airbags are labelled as ‘SRS’.

What does it feel like when an airbag goes off?

Given there is an explosive force inside each airbag, when one deploys it is a pretty dramatic event. The airbag inflating will be part of a collision, so you may not notice it as much as you might imagine among the forces and noise of the crash. That said, expect to hear a ‘bang’ as the airbag inflator detonates, while impacting with the airbag itself can, depending on the severity of the collision, feel like hitting a soft pillow.

You may experience ringing in your ears from the noise of the airbag deploying, while you may also find talcum powder on your body, as this is used to lubricate the device while it is stowed.

What about airbags and young children?

Rearward-facing child seats should never be put in the front seat of a car if the airbag is active, as the child’s head can be injured if the airbag deploys. Cars have ‘off’ switches for the front passenger airbag, but the rear seats are generally the safest place for children. If the child is in a front-facing child seat they can go in the front seat if they have to, but the passenger seat should be moved far back on its runners – check your vehicle’s handbook for more information.

Can airbags be dangerous?

The risks involved with airbags are far outweighed by the safety benefits they bring, but they are designed to work with occupants who are wearing seatbelts: they shouldn’t if it is detected that a seatbelt is not being worn, as they can otherwise cause injury.

it is also worth knowing about the Takata airbag recall. Airbags made by this company were fitted to around 60 million cars from almost every manufacturer, with a manufacturing defect potentially causing the explosive charge to detonate in an uncontrolled fashion. This could see the metal case the explosive is held in turn into shrapnel, which could be fired at vehicle occupants.

There have been no recorded fatalities in the UK as a result of this recall, but there remain a number of cars (most made from 200 to 2015) that have not yet been brought in for repair by their owners. This is why it is always a good idea to check if a car has an outstanding recall against it before you buy it, which can be determined by checking the Government’s online recall checker. If your car is affected by this recall, a replacement airbag will be fitted free of charge.

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