I appreciate the question OP. In fact, I appreciate it as much as I appreciate your comical user name. While it is an interesting question, it is unanswerable, as illicit Heroin's total composition is going to vary regularly. If we had a control in the form of constantly pure Heroin, things would be different.
I would put a large wager on Heroin vapor being generally harmless to the body, provided their aren't contaminants.