Direct-Vent Direct-Vent system uses two vent pipes. One draws air in from outdoors to support combustion. The other exhausts the by-products of combustion to the outside. The two vent pipes may be concentric (exhaust pipe within a larger diameter intake pipe) or co-linear (separate pipes of about the same size). Combustion takes place inside a sealed chamber – with a glass front in the case of a fireplace. Room air circulates around the combustion chamber, often assisted by a blower, to heat the room. A DV system is often installed along an outside wall to simplify the vent run, but can also be installed elsewhere in the home and vented through the roof. Advantages: Good efficiency – 60 to 80% Good heat output with thermal transfer through the glass and air circulation Separates room air from combustion air May be used as primary heat source Can operate with a remote or thermostat Most systems can provide live-saving heat during a winter power outage Choose fireplace, insert, cast iron stove, or heater