This is a helpful sanity check. So you see levels of 10-24ppm often as well? I mean these certainly don't *seem* dangerous and really aren't as far a getting deathly ill go, but I wonder about long term exposure. Or... is this just new information on account of these digital readouts and we *all* have been breathing these levels for many years? Yes, it's surprising how much CO a propane cooktop stove gives off... more than the wood stove... up to 30ppm, just like you said. No fresh air intake on this stove. It's a simple firebox going to single wall flue/chimney. Combustion air comes from the room, which, in turn, comes from all the cracks and air leaks around the boat.