A crash sensor triggers a tiny gas generator
An airbag’s speed comes from making gas on demand, rather than releasing air stored in a large tank. Sensors measure how quickly the vehicle is slowing and send that information to a control unit. If the crash is severe enough, the unit sends an electrical signal to an inflator inside the airbag module.
The inflator contains a small amount of solid propellant. The signal ignites it, and the rapid chemical reaction produces gas that fills the folded bag. In many designs, the gas passes through parts that help cool it and catch particles before it enters the bag. The process is controlled to inflate the bag in the brief interval when it can help protect an occupant.
The bag is designed to give way
Inflation is only half the job. As the occupant moves into the airbag, gas escapes through openings in the fabric. That lets the bag cushion the person instead of acting like a rigid balloon, while spreading the force of impact over a larger area.
Because deployment depends on the crash’s direction and severity, airbags do not inflate in every collision. They are designed to work with seat belts, not replace them: the belt helps hold a person in position so the rapidly expanding bag meets them as intended. What looks like a sudden burst is therefore a timed sequence—sensing, ignition, inflation, and controlled deflation—packed into a fraction of a second.
