Airbag (automotive restraint device)

How airbags work

Modern airbags rely on three main components: crash sensors that detect rapid deceleration, an inflator that produces gas, and the folded fabric bag. When sensors register a qualifying impact, they trigger the inflator which generates gas in a fraction of a second to expand the bag into the occupant space. The bag then cushions and slows the occupant's motion. Many systems are multistage or adaptive, varying deployment force according to crash severity, occupant size, and seat position. Airbags are described as Supplemental Restraint Systems (SRS) because they are designed to complement—not replace—seat belts.

Types and common placements

• Frontal airbags: for driver and front passenger, located in the steering wheel and dashboard.
• Side airbags: mounted in seats or doors to protect the torso in side impacts.
• Curtain airbags: deploy from the roof rail to protect heads in side impacts and rollovers.
• Knee and center airbags: protect lower limbs and reduce occupant movement.

Different designs and sensor networks coordinate to protect occupants from various impact directions. Inflators may use a rapid chemical reaction or stored gas to produce the inflation medium; designs have evolved to improve speed, reduce toxic byproducts, and manage inflation energy.

Airbags became widespread as passive safety technology advanced and regulatory programs encouraged their fitment. Over time manufacturers introduced smarter systems that reduce risk to children and small adults—examples include multi-stage inflators and disabling passenger airbags when a rear-facing child seat is detected.

While airbags greatly reduce severe injuries and fatalities when used with seat belts, they can themselves cause minor injuries such as abrasions or burns in some deployments and present higher risk to very small children placed too close to the bag. Recommended safety practices include always using appropriate restraints, keeping a safe seating distance from the dashboard, and following manufacturer guidance about child seating. Regular vehicle maintenance will help ensure sensors and airbags remain functional throughout the vehicle's life.