When Do Airbags Deploy? (Side, Front, Knee, Curtain + More)

When driving, knowing that you have a set of working airbags does a lot to provide you with confidence and peace of mind.

Your airbags, however, are rigged to only deploy in certain situations, but what situations would call for an airbag? Keep reading to find out!

When Do Airbags Deploy?

Most airbags deploy during an impact that’s equivalent to driving into a rigid wall at 8 to 14 mph (about 13 to 23 km/hr). This threshold is used to determine a “moderate to severe” crash, and any impact that doesn’t meet the manufacturer’s threshold will not trigger them to deploy. They also won’t deploy unless your car is running.

Keep reading to learn everything you need to know about the specific instances that cause your airbags to deploy, including specific airbags, types of crashes and more!

When Do Side Airbags Deploy?

Side airbags have a lower threshold for deployment because they’re installed in areas of the car where impact could make direct contact with the occupant.

Airbags can deploy in crashes that occur at as low as 8 mph when you hit a narrow object like a pole or a tree.

If you hit something wider like a wall or another car with your side, they could deploy at around 18 mph or 29 km/hr. They also deploy in frontal crashes that are severe enough that you would be flung around the cabin when the vehicle starts rolling.

When Do Front Airbags Deploy?

When Do Front Airbags Deploy?

Front airbags are what people usually mean when they talk about airbags in general, and they’re the ones whose instances of deployment are usually provided.

They will usually be deployed in crashes at between 8 and 14 mph that impacts the front area of the vehicle.

They will also be deployed for rear and side collisions if they’re strong enough, as well as when the car starts rolling.

Manufacturers have started installing front airbags with two thresholds that kick in depending on whether the person in the seat is using their safety belt.

If the belt is not latched, they would need more protection in the event of a crash, so the threshold is lower and vice versa.

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When Do Knee Airbags Deploy?

Knee airbags will usually deploy at the same time and for the same reasons as other front airbags.

When Do Curtain Airbags Deploy?

Like other forms of side airbags, curtain airbags will deploy in side impacts, such as when your car gets T-boned or you crash sideways into a tree, pole, wall, etc.

Curtain airbags will also deploy for severe front and rear end collisions and when the car starts rolling.

When Do Driver And Passenger Airbags Deploy?

Passenger airbags usually deploy from the dashboard at the same time as the driver’s airbag from the steering wheel.

There are some instances where the driver’s side airbags will deploy, but the passenger airbags will not, as discussed below.

When Do Passenger Airbags Deploy?

In recent years, manufacturers have been designing their vehicles to only deploy passenger airbags if their systems detect a passenger in the seat.

There are weight sensors underneath the seats that check for the presence of a passenger, and if they don’t detect one, they will disable the airbag on that side.

These sensors are also designed to read smaller weights to determine whether the passenger is a child or small adult, both of whom would be more susceptible to injury if an airbag on their side would deploy.

If they detect this, they will automatically disable the airbags.

When the airbag turns off in this case, the indicator light will come on, but it won’t if the airbags are disabled because there’s no passenger.

These sensors are the reason manufacturers discourage passengers in the back from pushing or pulling against the front passenger seat: because it interferes with accurate weight readings.

When Do All Airbags Deploy?

Airbags will usually deploy depending on the type of impact, and this means that if they deploy all at once, the crash is severe (e.g. it happens at a very high speed or the car begins to roll).

When Do Airbags Deploy In A Front End Collision?

In a front end collision, airbags will deploy if the crash happens at or above the threshold of between 8 and 14 mph on average.

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Do Airbags Always Deploy In A Crash?

Airbags will not always deploy in every crash, and this depends on several factors that don’t necessarily mean they’re faulty.

For example, if the crash happens below the required threshold for deployment then the airbags will not be activated.

Also, if they’ve been disabled either automatically by the system or manually after getting authorization from the NHTSA, then they will not deploy.

Airbags could also fail to deploy if the impact happens in an area of the vehicle that the sensors can’t detect.

If your vehicle doesn’t have side airbags and you get hit from the side, then front airbags likely won’t deploy.

They also aren’t likely to deploy if your car gets hit from the back, as discussed further below.

Do Airbags Deploy When Hit From Behind?

Do Airbags Deploy When Hit From Behind?

Airbags usually won’t deploy in a rear end collision because these types of crashes don’t cause the kinds of injuries that airbags can prevent.

When you get rear ended, the impact will force your vehicle to slightly accelerate and the inertia will push you backward.

What you’re looking at in a situation like this is whiplash, an injury that’s focused largely on the back of the neck.

Airbags won’t be of much help in this situation, which is why they’re usually not rigged to deploy when you get hit from behind.

Manufacturers install between one and three sensors on the car, none of which are in the rear, so it’s difficult to even detect impacts on that side.

There is an exception to this rule, however, which is that when you get rear ended incredibly hard, your front, side and other airbags might deploy because a strong enough impact could cause you to get flung around the cabin.

Do Airbags Deploy When The Car Is Not Moving?

If the car is running but stationery, then your airbags are still active and will deploy if you get hit.

This function is important for situations like impacts that happen when you’ve stopped at a red light.

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However, if the car is stationary but it’s off, even if the keys are in the ignition, the airbags will not deploy no matter how hard the impact.

What Triggers Airbags To Deploy?

Airbag systems rely on their sensors to tell them when they need to deploy the airbags.

These sensors are incredibly sensitive to abrupt and significant drops in speed, something that happens during a car crash.

Modern sensors also scan for the presence and weight of occupants in the car as well as changes in pressure that occur when the car is rolling.

When they detect a crash, they relay a signal to the electronic control unit (ECU) by completing a circuit, tripping another sensor, etc.

As soon as this signal reaches the ECU, a chemical explosion whose by-product is inert gas is created by the inflator.

This gas rushes into the airbag and inflates it instantly at around 200 mph or 322 km/hr, and the entire process is over in less than the blink of an eye.

How Much Force Do You Need To Deploy Airbags?

How Much Force Do You Need To Deploy Airbags?

As stated in the first section, airbags will deploy when you generate the kind of force that comes from hitting a rigid wall at 8 to 14 mph or faster.

How Do You Know If An Airbag Has Been Deployed?

If you get a used car and you suspect that the airbags have been deployed, you can check with insurance report platforms.

These platforms will let you submit a vehicle’s information and you can go through its history looking for reports of deployment.

If you are looking to learn more, you can also see our posts on how fast do airbags deploy, if airbags save lives, and how many airbags are in a car.

Conclusion

Airbags deploy at speeds of 8 to 14 mph (13 to 23 km/hr) or more but they can also deploy when stationary if the impact is strong enough.

Airbags in different areas of the vehicle could deploy even if the impact wasn’t concentrated around them if it was strong or if the car started rolling.

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