When you go shopping for gas fireplaces, you'll find that some gas logs are not vented. The blue flame of a vent-free gas fireplace unit is designed to provide nearly complete fuel combustion, resulting in less carbon monoxide and soot than a vented model. Byproducts of combustion simply enter the living space.
Unvented gas logs can be placed in a masonry fireplace, or in special fireboxes made to resemble a hearth.
Unvented gas appliances are always equipped with an Oxygen Depletion Sensor (ODS), which kicks the fuel source off before carbon monoxide reaches a dangerous level in the room.
Extra Moisture Water is a byproduct of combustion. In a vented appliance, most moisture escapes out the vent, but in an unvented unit it enters the living space. The extra humidity can be a plus for many homes during dry winter months, but if your home is tightly insulated the excess moisture may condense on cold windows.
Follow a Few Rules
Unvented gas fireplace appliances generate a lot of heat, so combustibles must be kept at a safe distance. Fireplace doors should be left open during use.
Never go to sleep and leave unvented gas logs burning. Most manufacturers recommend you only burn the logs for a few hours at a time.
Open a window slightly while the gas logs are burning, to let fresh air enter the room.
Bigger is not always better. For best air quality, the gas fireplace unit you install should be approved for the size of the room it will be used in.
Unvented gas appliances are not legal in all areas, so check your local building codes before buying a unit.
It's a good idea to install one or more carbon monoxide detectors, no matter what type of fuel-burning appliance you might have. Detectors are an inexpensive way to put your mind at ease about the air quality inside your home.
