How do I deal with smokers in a non smoking building.

[Samson Kay]

I rented to some tenants in September that are chain smokers. Although I didn't personally ask if the tenants smoked as part of my screening process, my lease clearly says no-smoking in the units. And because of how the building is ventilated the smell of smoke carries into the other units. So as a result I've gotten several complaints.

I've already warned them about smoking once before. Whats the best way to deal with this situation? Other than the smoking they are good tenants who pay on time. But the smoking is affecting my other tenants. I'd hate to have serve them a notice to vacate because of a bad habit.

What would you do?