How Do Ventless Fireplaces Work?

No Chimney

• Unlike a vented gas fireplace, a ventless fireplace does not need a fireplace or even a metal duct that attaches to the fireplace to transport the exhaust the fireplace produces. Because of this advantage, you may place a ventlesss fireplace in a room where you cannot fit a vented fireplace. No exhaust opening also means you may place a ventless fireplace in a room that is away from exterior walls and that has a story above.

Exhaust

• A ventless fireplace burns at an optimal level, which means it does not perform at its best. Working at the most optimal level, a ventless fireplace does not produce as much carbon monoxide or water vapor as a wood-burning fireplace or even a vented gas fireplace. An oxygen sensor on a ventless gas fireplace monitors the amount of oxygen in the room's air and adjusts the amount of gas the fireplace uses accordingly. Keeping the mixture of oxygen and natural gas at an optimal level allows the fireplace not to use a vent that runs to the building's exterior. Because a ventless gas fireplace does not allow its exhaust to escape to the outside, the fireplace may produce an increased amount of moisture inside its room's or home's air. During cold weather, this heated moisture can turn to condensation as it comes into contact with cold windows and exterior walls. As a result, poor vapor barriers in a house’s walls may lead to mold growth inside the walls.

Low Oxygen

• The oxygen sensor on a ventless fireplace is part of a design feature that shuts off the flow of gas to the fireplace if the amount of oxygen in the room dips below a predetermined percentage. Without this setting, the fireplace could burn the room's oxygen, leading to deadly consequences for any human or animal in the same room as the fireplace.

Heat

• Because wood-burning and vented gas fireplaces vent to a home's exterior, some of the warm air that those fireplaces produce flows through the chimney or exhaust pipe to outdoors. In contrast, ventless gas fireplaces do not lose heat to the outdoors because they do not connect to the outdoors in any way. All of the heat they produce stays inside the home.