The airbags are inflated by a pyrotechnic gas generator. Its basically a tiny rocket motor. It fires, burns for a few miliseconds and then expends its fuel and quits. The bag is hot because of the exhaust gasses.

the cloud is a combination of the inflation gas venting and lubricant. The air bags are designed to inflate rapidly and then deflate rapidly. They have vents sized to allow spring action on impact to absorb energy then deflate to get out of the way quickly. the lubricant is power. Used to be talcum powder that allowed the bag to unfold very rapidly without hanging up anywhere.

The circuitry that triggers the AB system is supposed to sense acceleration levels and NOT trigger unless they are sensed. But since your harnes failed massively all bets are off.

good job handling the emergency while in motion.