I've been using Mr. Heater Buddys for 16+ years. Have used one in 2 different FWC Granby's (1 full camper and 1 shell) and also an older Airstream. On my 2nd one now. Never had any issues with it them. As the video notes, I always have a window and the roof vent cracked to encourage air circulation. Also, I never sleep with it on. Have never noticed condensation problems with it. However, in cold weather, I have woke up to inside condensation on both the FWC and the trailer due to what 2 humans and a one or two large dogs put out. Also, have used it many times in a large family size camping tent. I think they are a great tool that is affordable and convenient, as long as one pays attention to how it is being used.