<P> The airbag provides an energy absorbing surface between the vehicle's occupants and a steering wheel, instrument panel, as well as the body pillars, headliner, and windshield . Modern vehicles may contain multiple airbag modules in various configurations including, driver, passenger, side curtain, seat - mounted side impact, knee bolster, inflatable seat - belt, front right and left side sensors and pedestrian airbag modules . </P> <P> During a crash, the vehicle's crash sensors provide crucial information to the airbag electronic controller unit (ECU), including collision type, angle and severity of impact . Using this information, the airbag electronic controller unit's crash algorithm determines if the crash event meets the criteria for deployment and triggers various firing circuits to deploy one or more airbag modules within the vehicle . Working as a supplemental restraint system to the vehicle's seat - belt systems, airbag module deployments are triggered through a pyrotechnic process that is designed to be used once . Newer side - impact airbag modules consist of compressed air cylinders that are triggered in the event of a side on vehicle impact . </P> <P> The first commercial designs were introduced in passenger automobiles during the 1970s with limited success and actually caused some fatalities . Broad commercial adoption of airbags occurred in many markets during the late 1980s and early 1990s with a driver airbag, and a front passenger airbag as well on some cars; and many modern vehicles now include six or more units . </P> <P> Airbags are considered a "passive" restraint and act as a supplement to "active" restraints, i.e. seat belts . Because no action by a vehicle occupant is required to activate or use the airbag, it is considered a "passive" device . This is in contrast to seat belts, which are considered "active" devices because the vehicle occupant must act to enable them . </P>

When did they start putting air bags in cars