By the one and only…

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How Do They Inflate?

Air bags are not inflated from some compressed gas source but rather from the products of a chemical reaction. The chemical at the heart of the air bag reaction is called sodium azide, or NaN 3 . Under normal circumstances, this molecule is quite stable. If heated, though, it will fall apart. The chemical equation 2 NaN 3 --> 2 Na + 3 N 2 describes exactly how it falls apart. Notice that the second product of the above reaction is N 2 , also known as nitrogen gas. A handful (130 grams) of sodium azide will produce 67 liters of nitrogen gas—which is enough to inflate a normal air bag. That's not the only chemistry involved. Notice that the other chemical into which sodium azide falls apart is Na, or sodium. Sodium is a very reactive metal that will react rapidly with water to form sodium hydroxide; as a result, it would be quite harmful if it got into your eyes, nose or mouth. So to minimize the danger of exposure, air bag manufacturers mix the sodium azide with other chemicals that will react with the sodium and, in turn, make less toxic compounds.

How Do They Know When to Inflate?

 There are sensors in the front of the automobile that detect a collision. These sensors send an electric signal to the canister that contains the sodium azide, and the electric signal detonates a small amount of an igniter compound. The heat from this ignition starts the decomposition of the sodium azide and the generation of nitrogen gas to fill the air bag. What is particularly amazing is that from the time the sensor detects the collision to the time the air bag is fully inflated is only 30 milliseconds, or 0.030 second. Some 50 milliseconds after an accident, the car's occupant hits the air bag and its deflation absorbs the forward-moving energy of the occupant.

Where Are The Airbags?

The Airbag Stored The Airbag Deployed

What Makes Up An Airbag System

   The bag is made of a thin, nylon fabric, which is folded into the steering wheel. The sensor tells the bag when to inflate. The collision force has to be equal to running into a brick wall at 10 to 15 miles per hour. A switch is flipped when there is a mass shift that closes an electrical contact, telling the sensors there has been a crash. The powdery substance released from the air bag, by the way, is regular cornstarch or talcum powder, which is used by the air bag manufacturers to keep the bags pliable and lubricated while they're in storage.