[sammyg2]

Never been around those plants but I've used a couple of industrial products that are similar.
Turbo seal and silver seal. Both are used on high temperature sealing on jet engines, high temp steam turbines, and gas expanders. Reportedly they use the sap from sumac in the manufacturing process.
the inside of my forearms broke out if I got within 5 feet of the stuff. I actually have scars from those products, little white circles that don't tan.
They've since come out with revised versions that are supposedly safer, I won't find out.