How Airbags Work
Written by Greg on August 1, 2014
According to reporting conducted by NBC News, the United States government has estimated that approximately 15,000 lives have been saved since the order on July 11, 1984 which required all vehicles to install driver’s side airbags, as well as through the extension of the law in 1989 to include passenger-side airbags. While we know that airbags certainly can save lives, and we are thankful for their presence, many may not how they work.
Not Just “Air”
While their name might suggest that airbags run by simply inserting a large amount of air in a contained space, there is more chemistry involved than this notion would have us believe. To start, the primary chemical involved is sodium azide, NaN3. Traditionally, this particular molecule is stable, however, when heated a chemical reaction can and will occur. According to research presented by Scientific America, the chemical equation used in airbags is 2NaBN3 – > 2 Na + 3 N2 which essentially produces nitrogen gas, which helps to inflate the airbag.
Additionally, Sodium is utilized has an extremely reactive metal that reacts with water to form sodium hydroxide. Naturally, exposure to these chemicals would not only create an airbag deployment, but they can also be harmful to humans. Thus, sodium azide is also mixed with other chemicals in order to make these chemicals less toxic.
Now that we know what chemicals involved and the overall process they react to, we might wonder what feature in the car kick starts these chemicals. In the front of the car, there are implemented sensors that will respond to a collision by sending an electrical signal to the area containing the sodium azide. After this occurs, the same electrical signal will then detonate, causing wave of heat to begin the breakdown of sodium azide before nitrogen gas then deploys in the airbag, causing it to inflate. The whole process occurs in approximately 50 milliseconds after the collision occurs.
It should also be noted that aside from electrical sensors, which has been outlined above, there are also mechanical sensors available, as well as slightly different variations of each. Some automakers utilize airbag igniter, which was mentioned above, while others will use electrical systems, often known as piezoelectric sensors that respond with switches, often located both inside and outside your vehicle. Finally, other automakers will use mechanical sensors which rely on small tubes that break when a certain pressure point is realized. This frees a gold ball that will complete the circuit and employ the airbag.
When the process is complete, and airbag will typically deploy in a matter of seconds, its speed differing on the make and model of the car. Moreover, airbags generally deploy at a speed of 100 – 220 miles per hour. As one can assume, this can cause severe injury if an individual does not stay at least 10 inches away from the airbag during deployment. Thus, you should take extra caution when sitting in a seat that has airbags, as well as ensure protection is kept in mind when seating children in the car.
Always remember that airbags are intended to supplement seatbelts and not be used in lieu of seatbelts.