Airbag Safety Concerns
Since the early days of auto airbags, experts have cautioned that airbags are to be used in tandem with seat belts. Seat belts were still completely necessary because airbags worked only in front-end collisions occurring at more than 10 mph (16 kph). Only seat belts could help in side swipes and crashes (although side-mounted airbags are becoming more common now), rear-end collisions and secondary impacts. Even as the technology advances, airbags still are only effective when used with a lap/shoulder seat belt!
It didn't take long to learn that the force of an airbag can hurt those who are too close to it. Researchers have determined that the risk zone for driver airbags is the first 2 to 3 inches (5 to 8 cm) of inflation.
So, placing yourself 10 inches (25 cm) from your driver airbag gives you a clear margin of safety. Measure this distance from the center of the steering wheel to your breastbone. If you currently sit less than 10 inches away, you can adjust your driving position in the following ways:
- Move your seat to the rear as far as possible while still reaching the pedals comfortably.
- Slightly recline the back of your seat. Although car designs vary, most drivers can achieve the 10-inch distance even with the driver seat all the way forward by slightly reclining the back of the seat. If reclining the seat makes it hard to see the road, you can raise yourself up by using your car's seat-raising system (not all cars have this!) or a firm, non-slippery cushion to achieve the same effect.
- Point the airbag toward your chest, instead of your head and neck, by tilting your steering wheel downward (this only works if your steering wheel is adjustable).
The rules are different for children. An airbag can seriously injure or even kill an unbuckled child who is sitting too close it or is thrown toward the dash during emergency braking. Experts agree that the following safety points are important:
- Children 12 and under should ride buckled up in a properly installed, age-appropriate car seat in the rear seat.
- Infants in rear-facing child seats (under one year old and weighing less than 20 pounds / 10 kg) should never ride in the front seat of a car that has a passenger-side airbag.
- If a child over one year old must ride in the front seat with a passenger-side airbag, he or she should be in a front-facing child safety seat, a booster seat or a properly fitting lap/shoulder belt, and the seat should be moved as far back as possible.
For more information about child car seats, read Car Seats: Fast Facts.
In certain special cases, car owners can request the ability to deactivate their airbags. In the next section, we'll discuss steps to take if you want to have your airbag deactivated.
The goal of an airbag is to slow the passenger's forward motion as evenly as possible in a fraction of a second. There are three parts to an airbag that help to accomplish this feat:
- The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door.
- The sensor is the device that tells the bag to inflate. Inflation happens when there is a collision force equal to running into a brick wall at 10 to 15 miles per hour (16 to 24 km per hour). A mechanical switch is flipped when there is a mass shift that closes an electrical contact, telling the sensors that a crash has occurred. The sensors receive information from an accelerometer built into a microchip.
- The airbag's inflation system reacts sodium azide (NaN3) with potassium nitrate (KNO3) to produce nitrogen gas. Hot blasts of the nitrogen inflate the airbag.
The airbag and inflation system stored in the steering wheel
Early efforts to adapt the airbag for use in cars bumped up against prohibitive prices and technical hurdles involving the storage and release of compressed gas. Researchers wondered:
- If there was enough room in a car for a gas canister
- Whether the gas would remain contained at high pressure for the life of the car
- How the bag could be made to expand quickly and reliably at a variety of operating temperatures and without emitting an ear-splitting bang
They needed a way to set off a chemical reaction that would produce the nitrogen that would inflate the bag. Small solid-propellant inflators came to the rescue in the 1970s.
The inflation system uses a solid propellant and an igniter.
The inflation system is not unlike a solid rocket booster (see How Rocket Engines Work for details). The airbag system ignites a solid propellant, which burns extremely rapidly to create a large volume of gas to inflate the bag. The bag then literally bursts from its storage site at up to 200 mph (322 kph) -- faster than the blink of an eye! A second later, the gas quickly dissipates through tiny holes in the bag, thus deflating the bag so you can move.
Even though the whole process happens in only one-twenty-fifth of a second, the additional time is enough to help prevent serious injury. The powdery substance released from the airbag, by the way, is regular cornstarch or talcum powder, which is used by the airbag manufacturers to keep the bags pliable and lubricated while they're in storage.