What Are Air Bags and How Do They Work?

These safety devices are, on balance, useful and necessary

Air Bags are passive restraints that activate when a vehicle senses a collision. Unlike seat belts, which only work if the driver or passenger buckles up, air bags are designed to activate automatically at the precise moment they are needed.

All new vehicles in the United States include front air bags for the driver and passengers, but many automakers go beyond that minimum requirement.

Airbags in an automobile cross-section
Lifewire / Brooke Pelczynski

Turning Off Air Bags

Air bags are designed so that they don't have to be turned on, but it is sometimes possible to turn them off. When a vehicle includes the option to disable the passenger-side air bags, the deactivation mechanism is usually located on the passenger side of the dash.

The disarming procedure for driver's side air bags is typically more complicated, and following an incorrect procedure can cause the air bag to deploy. If you are concerned that your driver's side air bag may injure you, your best course of action is to have a trained professional disable the mechanism.

How Do Air Bags Work?

Air bag systems typically consist of multiple sensors, a control module, and at least one air bag. The sensors are placed in positions that are likely to be compromised in the event of an accident, and data from accelerometers, wheel-speed sensors, and other sources feed the air bag control unit. If specific conditions are detected, the control unit activates the air bags.

Air bag safety demonstration with test dummy
Romilly Lockyer / Getty Images

Each air bag is deflated and packed into a compartment that's located in the dash, steering wheel, seat, or elsewhere. They contain chemical propellants and initiator devices that ignite the propellants.

When a control unit detects predetermined conditions, it sends a signal to activate one or more initiator devices. The chemical propellants are then ignited, which rapidly fills the air bags with nitrogen gas. This process occurs so quickly that an air bag fully inflates within about 30 milliseconds.

After an air bag is deployed, it must be replaced.

Air Bags Prevent Injuries

Because a type of chemical explosion activates air bags, and the devices inflate quickly, they can potentially injure or kill people. Air bags are particularly dangerous to small children and people who are seated close to the steering wheel or dash when an accident occurs.

According to the National Highway Traffic Safety Administration, there were around 3.3 million deployments of air bags between 1990 and 2000. The agency recorded 175 fatalities and several severe injuries directly associated with air bag deployments during that time. However, the NHTSA also estimated that the technology saved more than 6,000 lives during that same time frame.

That's a remarkable reduction in fatalities, but it's vital to use this life-saving technology properly. Short-statured adults and young children should never be exposed to a front air bag deployment to reduce the potential for injuries. Children under the age of 13 shouldn't sit in the front seat of a vehicle unless the air bag is deactivated, and rear-facing car seats should never be placed in the front seat. It can also be dangerous to place objects between an air bag and a driver or passenger.

How Air Bag Technology Evolved

The first air bag design was patented in 1951, but the automotive industry proved slow to adopt the technology. Air bags didn't show up as standard equipment in the United States until 1985, and the technology didn't see widespread adoption until years after that. Passive-restraint legislation in 1989 required either a driver's side air bag or automatic seat belt in all cars, and additional legislation in 1997 and 1998 expanded the mandate to cover light trucks and dual front air bags.

Air bag technology still works on the same basic principles that it did in 1985, but the designs have become more refined. For several years, air bags were relatively dumb devices. If a sensor was activated, the explosive charge was triggered, and the air bag inflated. Modern air bags are more complex, and many of them are automatically calibrated to account for the position, weight, and other characteristics of the driver and passenger.

Since modern smart air bags can inflate with less force or not at all if conditions warrant, they are typically safer than first-generation models. Newer systems also include more air bags and different types of air bags, which can help prevent injuries in other situations. Front air bags are useless in side impacts, rollovers, and other types of accidents, but many modern vehicles come with air bags mounted in other locations.

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