When you say publicly accessible buildings, do you mean government buildings? In that case, I think it would be reasonable.

If you mean any privately owned building that the owner wishes to allow public access to, then I think that is very unreasonable. If you don't like the smell of someone's building, don't go in- you don't have to accept their invitation to come in. You don't have to shop at their store. That would be like me coming to your house and telling you to stop smoking. You'd just tell me to leave if I don't like it. For many businesses, it is in their interest to create a smoke-free environment, so they do. But it should be the choice of the owner whether to allow it or not, not a government mandate. That's just wrong.