vents, we don't need no stinking vents
I hope your house isn’t very airtight.
“We have a delightful device called a ventless Natural Gas space heater. best money we spent on the house (East Tenn.)”
Be sure to have Carbon Monoxide detectors that work. As long as you have enough Oxygen, your heater will be perfectly safe with no CO. But if Oxygen starts to get depleted, then CO can form (from a different reaction)...and can kill you - unless your heater will shut off first (which some do).
Still a good unit (like 99% efficient), as long as you’ve got air communication with outdoors.
I have a Lopi Wood Burning Stove (pictured above) in my house. It heats @ 2400 SF which covers most of my house. We've had it since 1999 and have been using it every year since as our primary source of heat. We bring home our own wood every year from our property in Michigan's Upper Penninsula and recently brought home 3 cords of hardwood which will cover us from now until mid-March. Our furnace furnace is mostly for backup purposes so it doesn't get much use beyond the fan kicking on to circulate the warm air from the woodburner throughout the house. Our main cold-air return is in the same room as the woodburner (how convenient!)
Our house is 20 years old, so we're due for a new furnace and central air, now I'll make sure I replace it before May of next year to avoid all the bullsh*t.