Garage Heat
I first had an old mobile home furnace I hoisted up into the attic of the garage because it had the heat plenum facing down ( perfect for that setup) and ran it on propane. Worked good set up with a themostat, but it sure used a lot of propane. About 20 lbs in 6 hours.
Last winter I got a portable heater that works just as well to heat the 3 car garage, uses way less propane, but is kind of noisy when running. I can live with that. I can work in the garage for about 24 hours on one 20 lb propane.
I usually open the side door a crack after a couple of hours to make sure it is vented, but I think there is enough air infiltration that this may not be required.
http://www.northerntool.com/shop/tools/product_200178624_200178624