An air bag is a safety cushion that rapidly inflates during a car crash to protect people from injury. Hidden inside your car's steering wheel, dashboard, or side panels, air bags stay folded up and invisible until sensors detect a serious collision. Then, in less time than it takes to blink, a small burst of gas inflates the bag, creating a soft barrier between you and the hard surfaces of the car.

The technology is remarkable: the bag must inflate fast enough to cushion you before you hit the dashboard, but not so violently that the bag itself causes injury. Engineers designed air bags to work with seat belts, not replace them. Together, they've saved countless lives since becoming standard in cars during the 1990s.

After a crash, air bags deflate almost immediately so you can see and move. They're single-use devices: once deployed, they must be replaced. Modern cars have multiple air bags positioned throughout the vehicle, including side curtain air bags that protect your head during side-impact crashes.

The term appears as both air bag (two words) and airbag (one word), and both spellings are correct.