The airbag consists of a folded textile cushion designed to inflate quickly inside the vehicle immediately after a collision. Most airbags are inflated pyrotechnically and can only be deployed once.
There are four main parts in an airbag module (from right to left):
The airbag is controlled by the passive safety electronics unit that is normally located in the middle of the vehicle, where it is well protected. This "electronic brain" decides if and when each of the airbags should be deployed. It also controls the seatbelt pretensioners, providing the best protection for the vehicle’s occupants. The ECU receives information from sensors, such as accelerometers, mounted in key locations inside the vehicle. By measuring deceleration, accelerometers activate the airbag depending on the severity of the collision. Airbags are designed not to activate during sudden braking or while driving on rough or uneven pavement. In fact, the most severe braking is only a small fraction of the deceleration necessary to activate the airbag system.
The Airbag deployment
Frontal airbags are deployed in less than 50 milliseconds. Airbags for side protection have to be fully inflated within 15 milliseconds, which is eight times faster than the blink of an eye. Once an airbag deploys, deflation begins immediately as the gas escapes through vent holes in the fabric. A frontal airbag is empty after approximately one second.
Click here to learn more