Dear Shery, If you like, you might do a google search (www.google.com) for the effects of second hand smoke in pets. When I did, I found copious information related to your query, but I don't know how well justified it all is. From personal experience, we adopted two ferrets from a shelter maintained by a smoker who, like you, kept the windows shut. I think she went outside to smoke, but her husband did not. Just a guess, but I suspect the smoke-free environment in my home seems to have significantly improved the health of these two once very little and sickly guys, who are both now very strong and athletic, perhaps even too big depending on your standards. They are both five years old but act about 3, so this is truly a remarkable turnaround. I still worry over those left at the shelter, but a body does adjust some to it's environment. Take care, Kelly & MaryAnn [Posted in FML issue 4579]