My HVAC and water heater exhaust vent runs through my floor and through my spare bedroom closet, into the attic and through the roof. I am moving my daughter into this room from her nursary and the soon to come baby boy is taking her nursary. I have two fears: 1. There may be carbon monoxide leaking through the ducting and into the room, 2. This ducting gets warm, not sure how hot it gets and don't want this to be a fire hazard. I want to enclose it, caulk it and make it airtight, would this be a problem? With it getting warm/hot should I insulate it or use anything for fire protection?