How Air Bags Work

I read an interesting description of air bags, and was surprised to learn that they get quite hot when they expand. I thought gases cooled when they expand rapidly, but they choose a chemical reaction that gives off hot gases so that less chemical is needed to produce a given volume of gas, which I presume allows them to make a more compact device. I also found out that they use an electronic detection of rapid deceleration, rather than a mechanical one as in earlier models. I looked it up because I am surprised that there are not more reports of false detections and incorrect deployments.

"The airbag sensor is a MEMS accelerometer, which is a small integrated circuit with integrated micro mechanical elements. The microscopic mechanical element moves in response to rapid deceleration, and this motion causes a change in capacitance, which is detected by the electronics on the chip that then sends a signal to fire the airbag"

"Using hot gas allows the required pressure to be obtained with a smaller mass of gas than would be the case using lower temperatures. However, the hot gas can pose a risk of thermal burns if it comes in contact with the skin during deployment and occupant interaction. Burns are most common to the arms, face and chest."