Caution: Air bags present
December 1, 2005
Gone are the days when you would see only front-impact air bags in vehicles. Today, vehicle manufacturers add air bags and supplemental restraint systems to their cars to provide additional occupant protection during collisions. The average 2006 model-year vehicle offers four-to-six air bags as standard or optional components. The 2006 Toyota Camry, for example, comes standard with seven air bags, while the 2006 Hyundai Sonata has six. With approximately 60 percent of new vehicles featuring side-impact or side-curtain air bags, these safety innovations change the way auto glass technicians service vehicles.
Why so many air bags?
In 2009, the National Highway Traffic Safety Administration will require all passenger vehicles and light-duty trucks to pass a new side-impact crash test. The vehicle will crash into a barrier of the same approximate size at 20 miles per hour. In anticipation of this test, manufacturers are adding side and side-curtain air bags to their vehicles to provide additional side-impact protection. BMW’s new 7 and 5 Series models, for example, can be equipped with 10-to-12 air bags, including knee air bags in the lower dash.
Studies show that side-curtain air bags substantially reduce head and neck injuries, particularly for occupants seated alongside the air bag wearing seat belts. The Insurance Institute for Highway Safety in Arlington, Va., conducts side-impact crash tests. A vehicle crashes into a barrier the size of a pickup truck or sport-utility vehicle at 31 mph. According to IIHS officials, passengers in vehicles with side-curtain air bags suffer less severe injuries in side-impact collisions than those in vehicles lacking the technology. Air-bag manufacturers indicate that reduction may be up to 85 percent.
How do side air bags work?
Most side-curtain air bags utilize compressed argon gas, an inert gas stored in a pressurized cylinder called a hybrid inflator. The hybrid inflator is under 3,000 pounds per square inch of pressure. Side-impact air bags deploy approximately three times faster than frontal air bags at 0.12-to-0.25 milliseconds, with some approaching deployment speeds of 495 mph. The crush zone is smaller in a side-impact collision than in a head-on collision, so side air bags deploy faster than front-impact air bags.
Side-impact air bags deploy on the side of the vehicle where the impact occurs and protect the passenger’s head and thorax. Side-impact sensors mounted along the lower side of the vehicle detect intrusion at an impact speed of approximately 20 mph. The side-impact sensors may be located in the front or rear sides of the vehicle. They signal the diagnostic energy reserve module, or DERM, to deploy the side air bag in certain side-impact collisions.
Seat-mounted side air bags
Most vehicle manufacturers incorporate side-impact air bags in the outboard side of the front driver’s and passenger’s seats. Some locate side air bags in the rear seats. Look for the following labels along the seat back, base of the seat or on the trim of any head-curtain air bag: SRS, SIPS, air bag, SIR, IC or HPS. These labels indicate the location of supplemental restraint systems, side-impact protection systems, supplemental inflatable restraints, inflatable curtains and head protection systems, respectively. Side air bags in the front seats may be either head-thorax or thorax-size air bags, depending on the model year and restraint options. Most side air bags are 5-to-8 inches wide, 12 inches long and 12 inches tall. Head-thorax bags are 12-to-15 inches long and up to 24 inches tall.
Door-mounted side air bags
Some car manufacturers, including BMW, Cadillac, Land Rover, Mercedes and Porsche, incorporate side-impact air bags in the front and rear doors of their vehicles. The 2005 Porsche Boxster Carerra, for example, has a window air bag that inflates vertically up and out of the top of the door panel. Volvo also is expected to add a door-mounted inflatable curtain to the newly redesigned C70, available in 2006.
BMW tubular curtain
Most new BMWs come equipped with a head protection system. Look for the HPS label along the A-pillar trim of the vehicle. The air bag is anchored along the bottom of the A-pillar and extends to the rear anchor point behind the B-pillar. It is tucked up under the A-pillar trim and the headliner of the BMW. The inflation canister is located at the bottom of the A-pillar.
Head-curtain air bags
On cars, pickup trucks and SUVs without third-row seating, the curtain air bag deploys along the side glass in side-impact collisions and often remains inflated for 6-to-10 seconds. The curtain is usually a one-piece air bag approximately 5-to-6 feet long, 2-to-5 inches wide and 12-to-15 inches tall. The air bag is typically anchored at the front and rear pillars of the vehicle with tether anchors. The bag is mounted into the roof rail and folded into a flat roll under the headliner of the vehicle.
Many new SUVs, mini-vans and crossover vehicles with third-row seating are now available with third-row curtain air bags. These side-curtain air bags measure up to 8 feet long and 15 inches tall and deploy along the entire side glass of the vehicle, from the windshield to the back glass. Some models have a single hybrid inflator; others have two hybrid inflators along the side or mounted in the pillars of the vehicle. In addition, some vehicles feature segmented curtain air bags rather than one full-length curtain. Examples of vehicles with third-row curtain air bags include the Volvo XC90 seven-seater, Infinity QX 56, Nissan Pathfinder Armada and the Quest minivan.
In some vehicles, the curtain air bags will deploy in rollover crashes in addition to side-impact collisions. In 2002, Ford Motor Co. introduced the Safety Canopy System in some of its SUVs. It is now also available in some cars and minivans. Look for roll-sensing curtain air bags in Acura, Dodge, Chrysler, Ford-Lincoln-Mercury, Honda, Jeep, Mercedes, Toyota and Volvo SUVs. The new Acura TL, as well as the Ford 500/Mercury Montego, feature rollover curtain-sensor detection.