yep I use one, yes roll down ur window, at least 2 window, 2 inches, and get a carbon monoxide alarm for sure, run a small fan off ur battery, like one of those that they use on a computer. Now it will keep u comfy to a point, but not hot. If ur in 25 below stuff, it gets iffy, but I also have a generator and run 1500w of electric heat if I have to. with propane ur windows will sweat and sometimes moisture will drip from ur overhead , so I would insulate ur ceiling and walls too.