Thanks for the comments; Al, yes one of the modern high efficiency heaters where you just have a 3 inch vent through the wall might work. Was hoping for something on the cheaper side, but that would be a good investment. I probably have about any fuel I want but piping the NG would be a project. We are working on putting in electricity, so as Bob suggested it will be a possibility.( if I could talk my wife into her washer/dryer out there, she would make it plenty hot.)
Good info on CO and CO2, Steve. Didn’t realize that was the reason for change to the more modern ways of committing suicide. ( always thought the air injection was a joke— If you put out a cubic foot of exhaust at 10% CO2, then pump one cubic foot of raw air in with the first one, you end up with 2 cu.ft. with 5% CO2–??) Anyway, my shop is divided into a parking area and a 15x30 area to be heated. It is not insulated and with a walk in door, a window, and a 10 ft rolling door and a cold concrete floor, I don’t think moisture will be a problem. I will only heat the one area when I am in the shop. I agree about the noise, but I don’t know anything about those radiant heating systems. Saw a shop once that had a radiant tube/shield down the center of two bays. Don’t know how well it worked or what kind of gas they used.
In Ohio I had a 3 car garage as a shop, and I heated it with a 150,000 torpedo heater. It through out good heat – in a half hour or so I could take off my coat and until then I pulled it around where it blew on me. Pretty good deal except for hours after I could taste diesel fuel from my lungs. If I went with a torpedo heater it would have to be propane and yet I think that in your throat gives a taste. TomC