Greetings George,

In my opinion and experience, the smoke isn't there by itself.  It's a scent that is caught in a soul who is visiting you.  Do you remember anyone who smelled like that when they were alive?  Perhaps it's a friend who is checking up on you from the afterlife?

From all the experience you've been having with the non-physical, George, I think you can deal with this one just fine. 
All you have to do is find out who they are and what they want, right?
Then tell them that they'll be alot happier in the afterlife than hanging around stuck on Earth. There's alot more love for them in the afterlife than they'll ever get down here, for one thing !   You can convince them! 

When you smell the smoke again, think about asking a Helper to come and help take the soul back up to the Afterlife.  You must have some Helpers nearby anyway, since you are so often dealing with the afterlife.

I bet that once the smoker-soul gets up there, they'll meet so many people/souls they like that they'll be too busy to come back and pester you anymore. 

Bets