Last year I posted a small sign on my studio door:
Happily, I haven’t had occasion to enforce the policy since then, though I have previously had the occasional student who would have been in violation. It should go without saying that you shouldn’t ever show up to any college course or professional situation under the influence of any mind-altering substance, including alcohol, and my university also happens to be a “tobacco-free” campus, which is rare and awesome.
I wrestled a little bit with the “whether or not you were the one” clause, but it’s my workspace and I don’t like the smell of cigarettes, especially since my work involves a lot of deep breathing. Also, it means I don’t ever have to try to guess whether students are lying (not that any of mine would).
My students’ choices are their own, and I try to be extremely conscientious about not foisting my personal beliefs on them. However, I am also responsible to teach them to protect their health, at least as it relates to their woodwind playing, and to behave professionally. So fresh air—free of tobacco, alcohol, and drugs—is my policy.