An airbag is a type of safety restraint system used in automobiles. It is designed to inflate rapidly during a collision and provide cushioning for the occupants of the vehicle. Airbags are mounted in the steering wheel, dashboard, and door panels. When a vehicle collides with something, sensors detect the change in speed and send a signal to the airbag control unit. This unit initiates a chemical reaction that causes the airbag to inflate. The inflation process is extremely fast, and the airbag can deploy in as little as 20 milliseconds. The airbag is usually made of a fabric material that is folded inside the steering wheel, dashboard, or door. When it inflates, the airbag quickly expands and pushes out the fabric cover. The airbag will continue to inflate until it reaches its full size, which takes about 50 milliseconds.