Just as a completely different recommendation, we have for 8 years now used an Air-Dryer 500 when our trailer (cough, Airstream, not an Oliver 🙂 ) is parked in our pole barn in Central Florida. Intended for boats, it's basically a small space heater w/no moving parts. We crack both Fantastic Fans, and this little unit keeps the interior air "dry" enough with heating and air turnover to prevent musty odors and mildew. It does of course require 120v power. For 8 or so years before that we used a large compressor unit in our motorhome, and it did a good job as well. Never did get around to plumbing it, just emptied the tank every 10 days or so.
Hope this helps.
