Non-Smoking Trainers and Trucks?

What if I have asthma that is exacerbated (made worse) around cigarette smoke? Can I get a doctors note to request a non-smoked in truck?

I try to stay away from people smoking as much as possible. I realize that I'll come into contact with it sometimes, but to live in a smoked in "closet" would make me very ill.

For the record, I don't have a problem with people if they wish to smoke. I can always stand somewhere else where I'm not around it.