How to enforce a 'no smoking' policy in Chicago

[Kurt S.]

Hi. I am a live-in landlord to a 2-unit here. I suspect my tenant is smoking cigarettes in the unit below. It is a high end rental, and I planned to move in eventually, so I cannot tolerate this.

I added a 'no smoking in unit' clause to our lease, which they signed. The other day I was in their unit for an unrelated reason and the basement clearly smelled like cigarette smoke. I asked his partner if they were smoking, and she (verbally) admitted they were smoking marijuana in there, but denied cigarettes. I have never seen them outside smoking cigarettes. One time I smelled an old ash tray emptied into our garbage, but again they don't smoke outside. So where else would they be smoking but inside?

I'm absent any 'hard' evidence of them smoking, but I am almost certain they are. How should I proceed? They have 5 months left on the lease. I don't really want to wait that long if they are smoking. I would prefer them to leave early. Do I have grounds to terminate? They already admitted to smoking MJ, but it's really the cigarettes I don't want. But I don't have them admitting to that in writing or recording. How would you proceed in this situation?