I’ve been supplementing my shops heat with one of these this winter.
Fresh air intake for combustion, so it’s not consuming the oxygen from the shop and exhaust is routed outside. I have a carbon monoxide detector and have had no issues.
It goes through more diesel than the YouTubers claim, but it’s still a cheap way to raise temps to comfortable working conditions and because it’s not exhausting in the room no condensate issues either. I keep an electric heater in the shop to keep it above freezing, and turn on the diesel when I’m going to work in the shop.