CARBON MONOXIDE any concern??????
This is no different than the millions of propane and kerosene shop heaters used daily worldwide. It’s actually burns cleaner than those. All of these types don’t produce enough CO to register on detectors when properly functioning. Of course a CO detector is always a great idea in case something does go catastrophically wrong. I have tested it for nearly a week running 5+ hours at a time without opening any doors(intentionally trying to confine any potential CO).
Tested both on the floor where CO settles and at head height. The highest levels achieved were 13ppm directly in the path of the discharge heat port and 0ppm everywhere else in there shop. The 13ppm was only momentary and likely from initial fire up when the combustion isn’t perfect for a split second. Repeated and prolonged tests directly in the discharge path show ZERO. For reference OSHA permits workers to be exposed to 50ppm for 8 hours straight and 200ppm for short intervals. CO detectors usually don’t alarm unless they are exposed to 400ppm for over 5minutes straight. This is a SHOP/GARAGE heater and common sense should be used when using any heater that burns fuel or even electric.