Vented Gas Logs: Vented gas logs need to be burned in a wood-burning fireplace with the flue open, as they create some exhaust like burning wood does. The number one reason that people choose vented gas logs is that they look realistically like wood burning fires. That’s because of the way that the flames move, and the fact that they do produce exhaust like wood fires. The smell travels up the open flue, rather than circulating through your home.

There are two downsides to vented gas logs. First, because the flue needs to be open, heat is lost that travels up the chimney rather than heating the home. The other downside is that in creating these realistic flames and losing heat up the chimney, vented gas logs require more gas than their non-vented counterparts.

Vent-Free Gas Logs: Vent-free gas logs, also known as ventless gas logs, are similar to the vented gas logs, except that in this case, because you do not need to leave the flue open, the heat is dispersed more efficiently through the room. This makes vent-free gas logs much more energy efficient. These gas logs burn off water vapor and carbon dioxide. Because of the style, they do not look as realistic as the vented gas logs.