The ones which can be permanently mounted suck their air from the inner house, and thus work a lot more effectively. This portable unit of ours was dismantled and installed by myself before we left, and it now pulls air from inside our camper, and warms it, and sends it again out. All issues being equal, the air will get warmer in time and the
Alpha Heater official site slows down to keep up the temperature. I have seen these items installed on the inside of various setups, with the exhaust going via a gap, and outdoors (for apparent causes). I don’t like this, because the diesel tank is then inside, which smells, and can easily leak (our lid lately stopped screwing on tight), and while we used to transport it inside the canopy, I made positive it didn’t have a lot fuel inside as it was all the time a threat. I wasn’t keen on putting in the diesel heater earlier than we left, but I’m very glad we did. It’s so much nicer than having to lug a portable unit round, and its always ready to go when you want it.
