I was curious about this same thing. The building I work in is a 50x120 uninsulated metal quonset that's about 25ft tall at the center...so there's a snowball's chance in hell of actually trying to heat it. So my only chance is to just try and warm the spot where I'm working. My research led me to think that radiant kerosene is going to be the most cost effective way to be able to get work done during the winter months.
I picked up one of these yesterday at Tractor Supply Co and tried it out last night for a little while. I was pretty impressed with it. After the initial start up, which created a small amount of smoke, it ran very cleanly. I haven't been around a kerosene heater in many years, but the ones I was always created a smell. With this one, if I closed my eyes I don't think I would've been able to tell the difference from a propane heater. It's also not terribly loud.
It was only in the upper 40's last night but it heated a reasonable area. I will probably need 1 or 2 more to heat a useful amount of work space. I'm also going to remove the lower heat shield, or maybe even flip it around to the top, so that the heat travels farther before floating up. I'm going to mount it onto a dolly and may also slightly raise the back so the output is angled down a little.
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