Do I Need to Close the Chimney Flue if I Use Gas?

Gas Fireplace Insert

• Gas fireplace inserts fit inside an existing fireplace. Because burning gas can generate higher temperatures than burning wood, inserts typically include a chimney liner of stainless steel or aluminum. These inserts are referred to as fully vented systems. To burn gas in such a system, you need to keep the chimney flue open.

Direct-Vent Gas Fireplace

• A direct-vent fireplace is a standalone unit. Via pipes, it draws air from and vents exhaust to the outdoors. Consequently, this type of unit must be installed on an outside wall of the home. Because of the venting system, there is no chimney flue to worry about. Direct-vent pipes may be referred to as flues and, of course, must be kept open.

Ventless or Vent-Free Fireplaces

• Vent-free gas fireplaces are chimney-free standalone units that vent their exhaust directly into the room. Carbon monoxide safety concerns have prompted at least two states to outlaw the sale of ventless gas fireplaces. These systems are fitted with safety pilots that automatically shut off the gas when the room's oxygen level dips below a certain figure. Because no heat escapes through a chimney, these systems are considered heat- and energy-efficient.

B-Vent Fireplace

• A B-vent fireplace has its own chimney, or B-vent flue, and can be installed even in the center of a room. The flue is a metallic pipe that extends up to and through the roof. It can be costly to install. This type of fireplace draws oxygen from inside the room to help fuel combustion. Of course, the flue must be kept open in this type of unit.