Portable propane heaters consume oxygen, something the small interior area of a trailer or most other RVs don't have in great supply in cold weather. I'd never use a portable LP heater in such a limited space. An RV usually has a CO detector, and a smoke detector, but a properly operating portable LP heater will consume oxygen and your detectors won't give a beep. The LP furnace installed in most RVs is carefully designed to use air and exhaust the by products all outside the RV, never allowing anything by recirculated, heated air into the living quarters.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI