When I lived in Denver I used the Swingfire heater a lot, having the original installation in a 404 Unimog radio box. Having hot fresh air heat available when the snow and wind were swirling outside was wonderful. The heat exchanger provides dry heat, too, not steaming up the inside of the box like propane/catalytic does. But when that thing quits at 0213 in the AM and you have to go outside to restart it, you won't like it much, ha ha.
The joke was that by the time you pumped that handle long enough to start the heater, you were no longer cold.
I have a couple of those heaters I really need to referbish. The fuel evaporated from them over the years and they are nasty.
Good luck with yours.