For a graduate project I need to work together with a fellow student who smokes a lot (every time we take a break); the smell is really strong and actually distracts from the work at times. Some days we work from about 8am to 6pm together, which is quite a long time.
I'm not sure how to approach him about it, you can't really forbid someone to smoke, of course. Surely not for the duration of a whole day (I doubt someone who is addicted to it can go without for that long anyway). In a workplace setting, as ff524 mentioned, I might go to a manager, etc, but that is not always an option in academia.
In addition, I'm quite sure that he's unaware of this..