How Do Car Airbags Work?

What's the greatest thing since seatbelts? Airbags! Your risk of dying, if you are a driver in a head on crash, is reduced about 30%, provided you are wearing a seatbelt, and have airbags installed in your car. The first commercial automobile airbags started to appear on the scene in the 1980s, and since about 1998, have become standard features on both the driver and passenger sides.

When you experience a crash, your body is thrown forward with lots of momentum.(Objects in motion remain in motion.) Unfortunately, the car has come to a very sudden halt. A seatbelt can lessen the propulsion of your body, but at the same time, the belt can also cause serious injury, because of the impact of your body against it, at a high speed. This is where airbags can be so important. They can slow down the momentum of the driver and passenger. But they have to work very quickly, in order to prevent the driver and passengers from hitting the steering wheel, dashboard or windshield. The goal is to decrease the propulsion of the moving bodies to zero, but to do it with as little harm to the people in the vehicle, as possible.

Here's how it works. The bag is made of a nylon material, which is folded within the dashboard, steering wheel, and sometimes the seat or door. According to an article on CarJunky.com, there is a sensor that cues the bag to inflate, when the crash force is equal to running into a brick wall at 10 to 15 miles per hour.

This is where it gets a little technical. Sodium azide and potassium nitrate react to release nitrogen gas. The nitrogen gas discharges, and inflates the airbag. Apparently this happens at a speed of 200 mph, but then the gases immediately begin to escape through tiny holes in the bag, which allow it to collapse somewhat, enabling the victim of the crash to move. You can see the challenge-being solid enough to stop a fast moving body, and yet soft enough to cushion the impact. It has to deflate very quickly to prevent suffocation. And all of this has to happen within a fraction of a second!

Another challenge is to have the airbag inflate rapidly and forcefully, without a loud bang, which could damage hearing.

A great deal of science, experimentation, and computer simulation have been used to create the right design. Experts in geometry, thermodynamics, engineering, mathematics, and physics are needed to ensure that the airbag is designed correctly, and that it performs as required. Many different shapes are studied. And believe it or not, the folding and creasing of the airbag must be very precise. Various computer algorithms, (and even a form of origami) are used in the process.

Perhaps you have been concerned, (as I have), about the dangers of airbags to children and smaller adults (under 5'4"). An airbag often impacts them in the face or neck, instead of the chest, with an incredible initial impact. Anyone too close to the airbag is in risk of great bodily harm. (There are many cases of fatal injury from the airbag itself.) The driver should be approximately 10 inches from his airbag. (Keep in mind that almost all driver airbags are contained within the steering wheel.) The steering wheel should be angled toward your chest, not your head, neck, or abdomen.In the case of a child, it is suggested that all children under the age of 13, be restrained properly in the rear seat. A child should never be placed in a rear facing child safety seat, in the front seat of a vehicle with an airbag. The child would likely be crushed between the back of the front seat and the safety seat. (The newer airbag systems have a sensor that can determine if there is a person in the passenger seat, and if they are heavy enough for the airbag to inflate safely.)

For smaller adults, it is best to move the seat as far back as possible, while still being able to reach the gas pedal and brakes. (The obvious problem is, if you are short, (as I am), you have to be fairly close to the pedals.) It is also suggested that you may slightly recline the back of the seat, or use a cushion to raise your body into a safer position, with regards to the airbag. Because of many fatalities, and serious injuries to children and smaller adults, in 1997 the National Highway Traffic Administration decided to allow auto manufacturers to use less powerful airbags. And since 1998, dealers and car repair shops are authorized to install on/off switches, if a person is in a particular risk group. You should never attempt to deactivate an airbag on your own, as the airbag can mimic a bomb, and cause much harm, if you are not sure how to handle it.

Some people have expressed concern over seeing smoke when an airbag inflates, but it is actually powder or cornstarch that produces what appears to be smoke. They are used for lubrication to the bags, and to maintain flexibility.

Another great improvement, is that many cars are now being equipped with door mounted, and even seat mounted, side air bags. Some cars now feature six or eight airbags! But side mounted airbags have even less time to safely deploy, and very little car to cushion the impact. In a frontal collision, a good deal of the impact is absorbed by the bumper, the engine, and the hood. Not so in a side collision; there is only a thin door to minimize impact.

There is also now a head airbag, that is being included in many vehicles, and referred to as an Inflatable Tubular Structure. It is designed to stay inflated for about 5 seconds, in case there is an additional impact, as could occur in a rollover accident. There is also something called a curtain airbag for side collisions.

As you can see, the science and design of airbags is a work in progress. New technological advances are underway constantly, and the progress will continue to be amazing.

Sources: http://auto.howstuffworks.com/airbag.htm
http://www.topspeedracer.com/newsflash/how-vehicle-airbags-work.html
http://www.dmv.state.va.us/webdoc/safety/programs/airbags/index.asp
http://news.carjunky.com/how_stuff_works/how_air_bags_work_a198422.shtml
http://www.langorigami.com/science/airbag/airbag.php4