How to deal with bad smelling (smoking) co-student 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..
I believe the best thing to do is to be honest and tell him that the smell is very strong. 

Engage him in a discussion about smoking and ask him whether he has any plans to quit. From my experience every smoker wishes to quit. Then tell him that the smell is strong and sometimes you can't focus because of it. Take into account that this is maybe the first experience for him to work in a lab. Later on, he would definitely be aware of this, such as a non-academic workplace. 

Things you can do: 


Try not to discuss or meet right after smoking. 
Share gum with him.
Bringing air freshener to your office


In the end, there is nothing you can do if he's not willing to cooperate.

There are related questions discussing the same issue on Workplace.SE containing additional advice.