The dirtiest job I've ever had was as an industrial electrician in a copper wire mfg. plant. Very hot!! 120deg. general air temp. The copper dust and grease mixture that accumalates on the machinery. Mix that with carbon dust from the brushes on all of the d.c. motors, and you've got a nasty mixture.We would have to go in the back of these annealers and blow out all the carbon dust from the brushes that had worn down.When you get home and shower, you may wash your hair 3 or 4 times and still have black soot wahing out of your hair. I don't miss that place one little bit!!!