I have a “Ventless” gas / propane / kerosene heater. Is it Sealed Combustion?
Read the operating manual carefully. Unless there is a pipe penetrating the wall to outdoors for combustion air needs, and if the manual requires a window to be cracked open, it is not a Sealed Combustion unit. If a “cracked open” window is required, and you don’t open one because it’s too cold outside, you may be creating a recipe for tragedy.
