About "coking":

I think coking is the correct term. I spent a few years working at a refinery here in Houston - where there is a massive coking unit. After all the different fractions are squeezed out of a barrell of oil, they send the junk that's left over to the coking unit to pressure cook down into "coke", which comes out much like coal and is then sent to a cogeneration station to be burned for power for the refinery like coal. The coking unit is N-A-S-T-Y. The coke dust is very fine and gets into everything. They pay the operators extra to work the unit. I vividly remember talking to an operator who was telling me that, despite the high pressure showers they had, he would go home play tennis and "sweat black junk".

I stayed away from the place.