I use a buddy heater with a connection to a 20 pound tank outside. Only use it at night hunting or more when momma is camping. CO detector and roof vent open and haven't had a problem for 8 years and stay warm.
This right here. Our camper is so old it has "natural vents"!
We still crack the vent, but we did get ice on the windows.
The extra hose is worth every penny when you don't have to get up in the night and change a frozen propane cylinder.
