Look at camping world and the buddy and big buddy heaters. You can run a propane line into the Base camp with a flex hook up and have your propane tank sit outside. Both heaters have their own oxygen sensor thus will shut off if not enough oxygen.
We had the small one and it heated up our 21 GT no problem - we set it on the counter - out of way of the dogs - did not want them catching fire at night with their tails wagging
They are really portable and can be used with the small propane canisters so you can head to your favorite veiwing site and keep warm without making a big fire......