Open concept gas fireplaces heat the space by pulling fresh air from the outside into the room; the air then circulates throughout the room and is drawn back into the firebox and up the chimney. They are less effective than Direct Vent gas fireplaces and gas Inserts because they rely on the circulation and transfer of air rather than a convection process. They also are limited to a radiant heating process because blowers cannot be installed on Open Concept gas fireplaces.
They do however offer more flexibility in regards to temperature control. All woodburning and Open Concept gas fireplaces have a damper located inside the chimney; the damper controls how much air is released up through the chimney. It can be adjusted to either maximize the heat output of the fireplace and increase the temperature of the room, or decrease the temperature of the room, without affecting the aesthetic of the flame. This is not available with a Direct Vent gas fireplace; while some models offer the option of raising or lowering the height of the flame it is not as effective. The most efficient method of temperature control for a Direct Vent gas fireplace is to install a Thermostat that will shut off the fireplace when the room reaches the set temperature, but then the effect of the flame is lost.
Open concept gas log sets and pan burners with rock and glass media can be installed into existing masonry or brick fireplaces and zero clearance woodburning fireplaces. They are vented up through a chimney; masonry chimneys are typically built vertically or taper slightly then straighten out. Zero clearance woodburners have more vent run options but are still quite limited; the maximum allowable elbows for a zero clearance chimney varies from product to product.