How do Airbags work?

Why do we need Airbags?

When we crash our car, our heads can hit the steering wheel or other parts with an enormous force due to inertia. This can lead to death. So we need some cushioning effect that reduces the impact and injuries we face on such occasions. Hence, we came up with an invention called the airbag. There are several variations of the same, and the above is the most common one that is being used currently.

There are many variations in how an airbag can be designed. The following is one of them. Let’s jump in!

How do Airbags work?

Figure 1: Basic Airbag Circuit

1. When a car crashes, it naturally decelerates a lot during the impact. An accelerometer sensor detects the amount of deceleration that the vehicle is experiencing during the crash. You can read how an accelerometer works from my first email newsletter issue though it is not needed for understanding airbags.
2. If a large deceleration is detected, then it can be confirmed that a crash has happened. Instantly after this, a current is passed through a circuit which causes a thin resistance wire to reach a very high temperature. This part of the circuit is within your steering wheel, which also has the chemical Guanidine Nitrate filled in a cylinder as seen in Figure 1. All this happens in 2 milliseconds.
3. Guanidine Nitrate explodes at this high temperature and undergoes a chemical reaction to form liters of Nitrogen, filling a nylon bag placed within the steering wheel.
4. As the Nitrogen fills the bag, it expands within 20–30 milliseconds, saving the head from crashing into the steering wheel by acting as a cushion. The airbag pops out through the front panel of your steering wheel by opening it up through the explosive force.
5. There are holes in the back of the airbag away from you, through which the air can escape causing the airbag, to eventually deflate. After that, you can move around and not be constricted. This is how airbags work!

Figure 2: The two yellow connector points where the current passes through to explode the chemical within that cylinder (LEFT). The airbag is folded and placed inside the steering wheel panel (RIGHT). Source: Speedkar99

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