Air bags, an automatic crash protection system that deploys quicker than the blink of an eye, are the result of extensive research to provide maximum crash protection. Air bags by themselves protect only in frontal crashes, and offer maximum protection when used in conjunction with safety belts. Air bags should not be used as the only form of occupant protection; they are intended to provide supplemental protection for belted front-seat occupants in frontal crashes.
Typical air bag systems consist of three components: an air bag module, crash sensor(s), and a diagnostic unit. The air bag module, containing an inflator and a vented or porous, lightweight fabric air bag, is located in the hub of the steering wheel on the driver side or in the instrument panel on the passenger side. Crash sensor(s), located on the front of the vehicle or in the passenger compartment, measure deceleration, the rate at which a vehicle slows down. When these sensor(s) detect decelerations indicative of a crash severity that exposes the occupants to a high risk of injury, they send an electronic signal to the inflator to trigger or deploy the bag. The diagnostic unit is an electronic device that monitors the operational readiness of the air bag system whenever the vehicle ignition is turned on and while the ignition is powered. The unit uses a warning light to alert the driver if the air bag system needs service.
Air bags are designed to deploy (inflate) in moderate-to-severe frontal and near-frontal crashes. They inflate when the crash forces are about equivalent to striking a brick wall head-on at 10-15 miles per hour or a similar sized vehicle head-on at 20-30 mph. Air bags are not designed to deploy in side, rear, or rollover crashes. Rollover crashes can be particularly injurious to vehicle occupants because of the unpredictable motion of the vehicle. In a rollover crash, unbelted occupants can be thrown against the interior of the vehicle and strike hard surfaces such as steering wheels, windows and other interior components. They also have a great risk of being ejected, which usually results in very serious injuries. Ejected occupants also can be struck by their own or other vehicles. Since air bags provide supplemental protection only in frontal crashes, safety belts should always be used to provide maximum protection in rollovers and all crashes.
The bag inflates within about 1/20 of a second after impact. The inflated air bag creates a protective cushion between the occupant and the vehicle's interior (i.e., steering wheel, dashboard, and windshield). At 4/20 of a second following impact, the air bag begins to deflate. The entire deployment, inflation, and deflation cycle is over in less than one second. After deployment, the air bag deflates rapidly as the gas escapes through vent holes or through the porous air bag fabric. Initial deflation enhances the cushioning effect of the air bag by maintaining approximately the same internal pressure as the occupant strokes into the bag. Subsequent rapid and total deflation enables the driver to maintain control if the vehicle is still moving after the crash and ensures that the driver and/or the right-front passenger are not trapped by the inflated air bag. Dust-like particles present during the inflation cycle primarily come from dry powder that is often used to lubricate the tightly packed air bag to ease rapid unfolding during deployment. Small amounts of particulate produced from combustion within the inflator also are released as gas is vented from the air bag. These dust particles may produce minor throat and/or eye irritation. Once an air bag is deployed, it cannot be reused. Air bag system parts must be replaced by an authorized service dealer for the system to once again be operational.