I work maintenance at a chemical factory. One time we were taking out a system for maintenance and it was supposed to have been purged before we got there. All the paperwork was in order, so we went in as usual. Broke open the lines on the top and it smoked less than usual. The chemical in use has a flash point below zero degrees Fahrenheit and combusts on contact with water, so what's left in the pipes smokes when we open it. Oh, and the byproduct of combustion with water is hydrochloric acid.

Well we moved to the bottom of the main tank and started to open it and it had some major buildup inside, due to this we managed to completely separate the line before everything went to hell. The buildup broke and dropped well over a hundred gallons of chemical on us. Instantly the room is so full of smoke I could barely see to run. It splashed around my protective clothing a burned my skin. The reaction caused so much heat that I felt like it was already on fire. I knew it should have exploded already and ran for my life.

I escaped the building before the explosion that sent a 150-200 ft fireball out the side. I instantly ran to the nearest safety shower and stripped down. Luckily no one died, but we all went to the hospital with small patches of 3rd degree burns.