I would start by discussing with him. Taking a shower after smoking would eliminate the smell, and in a pinch a quick spray down with scentless Lysol would help. Treating the cause is far easier. If the smell seeps into the walls you can kiss goodbye to your security deposit.
As a smoker i would say that thats pretty unrealistic. Most smokers smoke at least 10 cigarettes a day, he would basically be pendeling between outside and bathroom. I would maybe rather suggest something like a smoking-jacket (or better a coat) that he puts on before smoking which doesnt enter the house besides for washing
I was responding to the way OP depicted his smoking as “every other day at night”. If they had just said their roommate smoked I would have interpreted it like you present it. Designated clothes are a good idea though. Scentless lysol works but for a chain smoker is going to burn a hole in the pocket.
My ex and I were pack-a-day smokers (out on the porch every 45 minutes to an hour, depending on activity). First hole in new pajamas was a rite of passage. Sometimes took a few months, but it always happened.