Burning flesh.
Worked at an industrial metal arts school. (Blacksmithing, welding, foundry, etc.) Students were told not to wear polyester socks. And if they had forgotten, we gave them duct tape to cover up their socks.
One year, a student came to school wearing polyester socks. But didn’t follow proper safety protocol.
Spark hit his sock. Burned right through the polyester and started melting the polyester onto his skin.
I will never forget that smell.