i had vent covers (like Maxx Airs) put on my TT and leave the vents open. I keep one or two of the Damp Rid containers that are about 3-4 cup size in my 28 ft TT. I do try to open the doors when I am outside and around the trailer at least for a bit most weekends. Damp Rid has a regular one and one with charcoal that I am using right now, since we have had so much rain; the containers are doing the trick to keep it smelling fresh. I was in trailer this morning and was carefully smelling for any musty/damp smells as DD, SIL and 1 month old GD will be staying there for a week while they are visiting. (DD chose to stay there for privacy of guest house).