How do airbags work during a collision?

Airbags deploy when crash sensors detect rapid deceleration exceeding a threshold (typically 15-30g). The sensors send a signal to the airbag control unit, which triggers an igniter that burns a solid propellant (usually sodium azide), producing nitrogen gas that inflates the airbag in 25-50 milliseconds. The bag then deflates through vent holes as the occupant contacts it, absorbing energy gradually and reducing head and chest injury severity.