A Complete Guide to Car Airbags

Since their introduction back in the 1980s, airbags have become an indispensable car safety feature in the UK, preventing countless injuries and saving many lives. Today, it's impossible to imagine vehicles without these protective cushions that inflate rapidly in the event of a collision - one that UK law has now made mandatory. 

Whether it's the familiar driver and front passenger airbags, or sophisticated ‘side curtain’ and other types of airbags found in brand new cars, their function remains vital - cushioning otherwise violent impacts to dramatically reduce the risk of severe injury and fatality. 

In this complete guide to car airbags, we discuss what rules airbags are bound by, reveal how they work, and discuss how safe they really are. Read on to find out more… 

What are the rules for airbags in cars?

All new cars sold in the UK must be fitted with front airbags for the driver and front seat passenger as standard - this has been a legal requirement since 1998. Since 2003 however, all newly manufactured cars must also have side-impact protection airbags that keep the head and chest safe of front seat occupants in the event of side-on collisions. These types of airbags are commonly called ‘side curtain’ airbags.

Currently, there are no mandatory requirements for rear seat airbags, knee airbags, or rear side airbags to be fitted, but many new cars now include some of these as optional extras. It’s worth knowing that it is illegal to deactivate any airbag in a vehicle or install a switch that allows manual deactivation unless carried out by an authorised technician for specific medical exemptions.

In addition, airbag warning lights must work as intended by the manufacturer - it is an offence to tamper with them in any way. An annual MOT test will check that airbag warning lights work effectively. When airbag systems need replacing, only original equipment manufacturer-approved parts can be used in order to ensure they meet current safety regulations. 

What types of car airbags are there?

The most common types of airbags found in cars are:

Front airbags

The driver and front passenger airbags are installed in the steering wheel and dashboard. These protect the head, neck, and chest in the event of frontal impacts.

Side airbags

Mounted in the seat or door frame, these protect against impacts from the side. Types of side airbags include:

• Side torso airbags that protect the ribs, chest, and abdomen.
• Side curtain airbags that release downwards from roof linings to protect the head
• Side tubular/inflatable airbags that typically contain two or more small airbags

Knee airbags

These are installed underneath or within the dash and are designed to reduce leg and knee injuries.

Rear airbags

Optionally found in the rear seat, they can also include rear-side airbags and curtain airbags in some makes of cars. These are specifically designed to help protect children.

Seat cushion airbags

These clever types of airbags are stitched into the seat bolsters and can be included in both the front and rear seats. 

Centre airbags

Also known as ‘front centre’ airbags, they inflate between the driver and passenger to prevent front occupants from colliding if the car is involved in a crash.

How do car airbags work? A step-by-step guide

Car airbags work through a complex sequence of events that unfold extremely rapidly (within a fraction of a second!) in order to protect the occupants of a vehicle in a crash. Below we’ve highlighted the six key steps of an airbag in operation:

1. Crash Sensors - Sensors mounted around the front and sides of the car detect a sudden reduction in velocity, which is typical of an impact. This sends an electrical signal directly to the airbag control unit.
2. Airbag Control Unit - The signal is processed by the airbag’s electronic control unit which activates the airbags if thresholds indicate a severe crash.
3. Inflator Ignition - The electronic control unit then triggers an electrical current to ignite the sodium azide propellant in the inflator of the airbag. 
4. Chemical Reaction - Next, the sodium azide undergoes an explosive chemical reaction which rapidly produces nitrogen gas to inflate the nylon or polyamide airbag.
5. Bag Inflation - The nitrogen gas inflates the airbag at a speed of over 200 mph, with the full inflation process taking milliseconds (approximately 0.03 of a second!).
6. Deflation - Tiny holes in the airbag allow the gas to escape and deflate immediately so the occupant does not rebound off it with too much force.

How safe are car airbags?

Car airbags are very safe and effective lifesaving devices in most collisions. However, there are some important things you should know about their safety when it comes to your daily car journey:

• Airbags deploy with considerable force (around 200 mph) so they can cause injury in some situations - most injuries are minor.
• Airbags can be hazardous to children sitting in the front seat, particularly infants in rear-facing child seats. The safety recommendation is children 12 and under should be properly restrained in the back seat.
• For adults, sitting too close to the steering wheel or dashboard (less than 10 inches away) increases airbag injury risk. Drivers should sit upright and at least 10-12 inches distance from where the airbag is fitted.
• Most new vehicles have advanced airbag systems with multiple stages of deployment. Occupant detection systems are designed to optimise the effectiveness of airbags to minimise injury risks.
• Following vehicle manufacturer guidance on correct seating position and wearing seat belts properly is the best way to stay safe with airbags. 

Are car airbags a legal requirement in the UK?

Yes, it is a legal requirement for a car to have airbags fitted in the UK. This has been mandatory for all new cars sold since 1998 under safety legislation and includes front driver and passenger airbags as standard. Since 2003, side-impact chest and head protection airbags for front seat occupants have also been a legal requirement for new cars. These are often in the form of side curtain airbags.

There are currently no UK requirements for rear seat airbags, knee airbags, or rear side airbags - those remain optional extras in most cars. It is also against the law to remove or deactivate a factory-fitted airbag on a vehicle in the UK, unless carried out by an authorised technician for approved medical exemptions. This includes dismantling the airbag system or installing an off switch.

Does a faulty airbag cause a car to fail an MOT in the UK?

Yes, a faulty airbag will cause a car to fail its MOT test in the UK. One of the inspection items during an MOT is checking that airbag warning lights perform as intended before and after the engine starts up. Any airbag warning lights that fail to operate, indicate a fault or warn technicians that airbags have been deactivated which means the car will automatically fail the MOT.

In addition to the warning lights, visible missing or deployed airbags without replacement and faults with the actual airbag crash sensors also constitute MOT test failures. The only exception is if an exemption for airbag deactivation has been granted by vehicle examiners for approved medical reasons, although paperwork must provide evidence of this.  

How much does it cost to replace a car airbag in the UK?

The typical cost to replace a car airbag in the UK ranges from £200 to £700 or more, depending on the airbag type and vehicle model. Driver or front passenger airbag replacement averages £200-£350 for the part and fitting. 

More complex airbag installation on higher-end cars may exceed £500. Airbag control units cost anywhere from £150-£300 depending on the complexity of the device, while crash sensors usually range from £60 up to about £120 each.

While replacing airbags may seem costly, it helps ensure occupant safety in an accident and avoids MOT test failures from malfunctioning systems. Using approved original equipment parts is also crucial for proper performance.

New and used cars for sale with airbags

Here at EMG Motor Group, we proudly sell both new and used cars and have a huge selection to choose from. Our cars come equipped with airbags for ultimate safety for you and your passengers. 

Whether you’re searching for an SUV, estate, hatchback, or 4x4, our helpful and experienced team can guide you toward the ideal vehicle to suit your needs. We have 11 branches across East Anglia where you can visit us in person, or explore our entire selection of stock via our online showroom - the choice is yours.