We were on the Fantasy and I asked the exact same question because my husband is very sensitive to smoke. I e-mailed Carnival and was told they deodorize all rooms between cruises. Now whether that is actually true, I don't know, but I can tell you there was no odor of smoke in our cabin. The dining rooms and main show lounge (on the Fantasy this is the Universe Lounge) are smoke-free. Avoid the casino areas, the bars, and outside decks near the placement of mounted ash trays. We communicated with a Carnival Representative a few times by e-mail. She seemed very happy to try to accomodate us. Good luck and have a great time!