Question: We have a couple of employees who smoke and have recently moved into an office next to someone who doesn't smoke and finds the odor unpleasant. What are best practices for handling a situation like this?
Answer: A best practice is to discreetly coach and counsel the employees who have the offending odor and to offer accommodations to the employee with the complaint. An accommodation could be a fan or air purifier if the complaint continues.
As an employer, you can treat this as you would any other performance issue. The best practice is to point to any dress code and/or hygiene policy you may have that (hopefully) provides language about odors or a clean appearance.
Hand washing, wearing a jacket outside to smoke and removing it before coming back in, and/or waiting a few moments before coming back inside after smoking are other ways smokers can try to lessen the odor.