The "airbag" was developed by American industrial engineer John W. Hetrick, who patented and built the prototype on his kitchen table in 1952. The design resulted in a gas-filled envelope that can be automatically extended to cushion passenger impact during a car crash. Breed Corporation took Hetrick's original work and enhanced the design by adding various active trigger sensors. This lead to the airbag's internal development in conjunction with various "Big Three" companies in the late 60's, with a first production roll-out in GM's Buick Electra line in 1974.
Airbags are operated on the basis of three components: An airbag module; one or more crash sensors, including an accelerometer; and a managing diagnostic unit. The front airbag is contained in the steering wheel, with a secondary dash panel bag on the passenger side above the glove box.
Side airbags are located in the headliner on either side of the passenger compartment. The intent of these devices is to mitigate the impact of a sidewards movement in a crash.
Knee airbags can be carried under the passenger glove box, and also under the back of the front seats. The intent is to limit knee impact in the event of an accident.
Rear curtain airbags are designed to drop down behind the rear passenger compartment, to primarily cushion the impact of a rear-end collision.
Regardless of the make of the car, or position of the device, airbags typically extend between 10 to 25 milliseconds after collision. The impact threshold for the process is based on a transient impact of 5 to 7g, at a crash speed of between 5 to 15 mph. The variance is based on several factors, including angle of impact, its characteristics (meaning a direct, or deflected secondary hit), transient velocity, or other pressure metrics, as established by the on-board airbag system instrumentation. While these devices do reduce crash fatalities, there are some potential downside impacts in the case of slower speed incidents. These can include abrasions of the face and body, bruising, or in certain circumstances broken bones.
