> A sealed house with a fire burning in it is a suicide machine. Modern designs use direct vent systems, where instead of using inside air for combustion, they

> A sealed house with a fire burning in it is a suicide machine. Modern designs use direct vent systems, where instead of using inside air for combustion, they bring in outside air (and then exhaust externally as usual): * https://www.efireplacestore.com/five-things-about-direct-vent-fireplaces.html https://www.efireplacestore.com/five-things-about-direct-ven... The warming of the house occurs via radiant heat and through any conduction of heat via the actual material of fireplace or stove.