This is the one i use to keep my RO warm but my RO is inside garage then inside a wooden box that i made, this is for cold night going to like minus 4-6 works fine keeps the box at around 5-8 c constantly in the night.
This burns with a yellow flame but i dont get any soot at all a slight smell but nofifng too bad so not sure what Ian actully ment altho those others are diffrent i think that crystal-clear linked up.