This should be a conversation starter!

I personally don't think the guy smoking would affect his ability to do a good job? Would you rather have a brilliant painter & decorator who smokes or a crap one who doesn't?  (Dunno how good or bad he is at his job?)

If you were worried about passive smoke, you would only need to stay out of the room he was working in until he was finished.

As veggie says, I would offer him a cup of coffee, then skidaddle.