I can speak from personal experience that a very steamy shower and/or an overly sensitive smoke alarm can trigger the alarm. We had a hard wired alarm right outside of our bathroom and we learned not to shower with the door open for fear of setting it off. Many hard wired alarms can be adjusted to be less sensitive. If they can't cite proof of your smoking other than the alarm, I would definitely fight it to the end...

Out of curiosity, does anyone know what the policy is on candles in the room? (In relation to the smoking policy.) Do you think they'd try to charge for snuffing out a candle? (sans alarm )

Thanks and good luck!