This time last year (as soon as the weather started warming up) my CO/Propane detector started going off. Nothing I could do would silence it other than keep all windows open and ceiling vent fans running. I did have a foul odor inside. After driving myself crazy I turned off the propane completely and disconnected the detector. It finally occurred to me what the small was. A critter of some type crawled into my underbelly and died. When the weather warmed up the methane gas from decomposition set off the detector. I never found the remains, but after about 10 days the smell went away and I turned my propane back on and rewired the detector. I did have a colony of chipmunks living around me. They are all gone now thanks to a .22 pellet rifle and a nice scope.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof