Reply #11: The volatile portions of the oil evaporate. That is why they are called volatile.

[JDPriestly]

Portions of the oil do evaporate, and presumably, the chemical nature of those evaporated portions changes as the evaporation takes place. My question is what does the evaporated oil change to? Just curious. I doubt that it is dangerous after evaporation. If evaporated oil remained extremely dangerous after evaporation, people would not be able to work in gas stations or at refineries. They do. It's dangerous work, but people do work in those situations sometimes for many years. And, of course, people live in areas in which crude oil is being pumped out of the ground. In fact I believe that we have productive oil wells right here in Los Angeles.