Airbag Functionality: How It Works in a Crash

May 11, 2025

Airbag Functionality: How It Works in the Event of a Crash

When it comes to vehicle safety, the airbag is one of the most crucial innovations in modern automotive engineering. It’s something you rarely think about—until it saves your life. But have you ever wondered how an airbag actually works? What happens the instant your vehicle is struck, and how does that soft cushion deploy fast enough to make a difference?

Let’s pull back the curtain on airbag functionality and break down exactly how these lifesaving systems operate when seconds count.

What Is an Airbag and Why Is It Important?

An airbag is a vehicle occupant-restraint system designed to rapidly inflate during a collision, providing a cushion that helps prevent injury. It’s not there for comfort—it’s there for impact protection.

While seat belts are your first line of defense, airbags act as a backup to reduce the force on the body, especially the head and chest, during a high-speed crash.

Why Do We Need Airbags?

To reduce head and chest trauma in frontal or side collisions
To spread out impact force across a larger area of the body
To prevent contact with hard surfaces like the steering wheel, dashboard, and windshield

Here’s the thing: without airbags, even a properly worn seatbelt can’t always stop forward motion fast enough. Airbags are timed to act in milliseconds—right when you need them most.

How an Airbag System Detects a Crash

So how does your car know when to deploy the airbags?

At the core of airbag functionality are crash sensors, typically accelerometers, which detect rapid deceleration. These sensors continuously monitor the vehicle’s movement and respond when a significant change—like hitting another car or object—occurs.

Key Components Involved in Detection:

Crash Sensors: Measure sudden deceleration
Airbag Control Module (ACM): The brain of the system that makes deployment decisions
Impact Threshold: A specific “G-force” level that, if exceeded, signals deployment
If the threshold is met—usually equivalent to hitting a wall at 10–15 mph—the ACM triggers a chemical reaction to inflate the airbags.

What Happens in the Split Second of a Crash?

Now let’s walk through what actually happens in those first milliseconds of a crash.

Sensor Activation (0–20 ms)
Crash sensors detect rapid deceleration and send a signal to the control unit.
Signal Processing (20–30 ms)
The control unit analyzes the data. If the situation meets airbag deployment criteria, it sends an electrical signal to the inflator.
Airbag Inflation (30–50 ms)
The inflator ignites a small amount of sodium azide or another gas-generating compound. This rapidly creates nitrogen gas that fills the airbag.
Airbag Deployment (50–70 ms)
The airbag bursts out of its housing—steering wheel, dashboard, seat, or side panel—and inflates fully in about 1/20th of a second.
Occupant Contact (70–100 ms)
By now, the occupant is still moving forward and meets the fully inflated airbag. The airbag begins to deflate immediately to absorb energy.

This entire sequence wraps up before you even realize what’s happened.

Different Types of Airbags in Modern Vehicles

Most people associate airbags with the steering wheel and passenger dashboard, but modern vehicles are equipped with multiple airbag types, each designed for different types of impact.

Common Airbag Types:

Airbag Type	Location	Purpose
Frontal Airbags	Steering wheel, dashboard	Protect head and torso in frontal crashes
Side Airbags	Inside seat or door panels	Protect ribs, pelvis, and chest in side impacts
Curtain Airbags	Roof lining above windows	Prevent head injuries from glass/side impacts
Knee Airbags	Beneath dashboard	Reduce leg injuries and improve posture on impact
Rear Airbags	Rear seats (less common)	Protect rear passengers

Some newer models even include pedestrian airbags that deploy on the exterior of the vehicle to cushion impact with pedestrians. Pretty incredible, right?

How Safe Are Airbags Really?

According to the National Highway Traffic Safety Administration (NHTSA), frontal airbags saved over 50,000 lives in the U.S. between 1987 and 2017. When combined with seat belts, they reduce fatal injuries in frontal crashes by up to 60%.

But like any system, airbags aren’t perfect.

Potential Risks:

Airbag Burns: The hot gases used in inflation can cause minor burns.
Injury from Improper Positioning: Sitting too close to the steering wheel or dashboard increases the risk of injury from airbag deployment.
Children and Airbags: Airbags can be dangerous for small children. That’s why kids should always ride in the back seat.

To minimize risk:

Keep at least 10 inches between your chest and the steering wheel.
Always use seat belts properly.
Place rear-facing child seats in the back seat only.

How Airbag Systems Are Tested and Regulated

Airbags go through intense scrutiny during vehicle development. Automakers must comply with strict regulations to ensure airbags deploy only when needed—and not when they shouldn’t.

Testing Procedures Include:

Crash Test Dummies in frontal and side-impact tests
High-speed sled testing
Deployment timing verification
Environmental testing (extreme temperatures, humidity)

Manufacturers also run computer simulations to test airbag scenarios before any real-world crash test even happens.

If you'd like to learn more about crash testing, [link to "Crash Testing Explained: How Vehicles Are Rated for Safety" here].

Maintenance Tips: Keeping Your Airbags Functional

Unlike oil or brake pads, airbags don’t require regular maintenance—but there are still a few things you should keep in mind.

Airbag Maintenance Tips:

Dashboard Light: If the airbag light stays on, get it checked immediately. It could mean your airbags won’t deploy in a crash.
After a Collision: Airbags can’t be reused. Once deployed, they must be replaced.
Buy Cautiously: If you're buying a used car, ask for airbag service history—especially if it’s been in a previous accident.
Avoid Tampering: Never disable or modify your airbag system unless it’s under professional guidance (e.g., for child seats).

The Future of Airbag Technology

Airbags are evolving fast. As vehicles move toward autonomous driving and advanced driver-assist systems, airbags are getting smarter, faster, and even more protective.

Upcoming Innovations:

Adaptive Airbags: Use sensors to adjust inflation force based on the occupant’s size and position.
Far-side Airbags: Deploy between the driver and front passenger to prevent collision between occupants.
External Airbags: Being tested for use outside the car to soften impact with pedestrians or during side collisions.

In short: the humble airbag is becoming a high-tech guardian.

Final Thoughts: Don’t Overlook the Airbag

The airbag might not be something you think about when you hop into your vehicle, but it’s quietly standing by—ready to protect you in the worst-case scenario. Understanding how this system works isn’t just interesting; it helps you stay safer on the road.

And let’s be honest: you never want to need your airbags, but when you do, you’ll be glad they’re there.

Want to make sure your airbag system is functioning properly? Visit your trusted auto repair shop or contact a certified airbag service specialist for an inspection—especially if your airbag light is on.