Ventless Gas Fireplaces

Who doesn’t love a fireplace on a cool evening? There are many options to create that atmosphere other than wood-burning fireplaces (and all the maintenance that comes with them). An option that many homeowners find very attractive is the ventless gas fireplace.

Ventless fireplaces, more accurately known as duct-free fireplaces and room-venting fireplaces, are a type of residential gas-heating device.  These kinds of fireplaces are preferred because they burn at nearly 100% efficiency. This means they release far less harmful gases than most other portable heating alternatives. And their installation is restricted little by architectural constraints.

Not Without Controversy

They are controversial, however. Despite their name, they vent unburned combustion byproducts directly into the living space. Traditional fireplaces, by contrast, are equipped with a flue that vents to the outdoors. These flues save the home’s occupants from exposure to the bulk of the carbon monoxide (CO) and airborne particulates created by the fire. As a less serious yet still important side note, ventless fireplaces create high levels of water vapor. This can lead to mold growth and a variety of other moisture-related building problems. Mold can be a serious health hazard for at-risk individuals, and it can damage fabric, photographs, books and building materials.

Mitigating the Dangers

To mitigate CO dangers, manufacturers instruct customers to keep a window open while ventless fireplaces are in operation –- advice that is easy to ignore, as an open window allows the entry of cold air, defeating or diminishing the efforts of the fireplace to warm the living space. Many manufacturers also install an oxygen-detection sensor (ODS) in their ventless fireplaces that will automatically shut down the appliance if oxygen levels in the home become dangerously low. Critics point out that this sensor is typically located at the lower part of the unit near the floor, where it detects cool, fresh, oxygen-filled air and misses hot combustion gases as they rise and pool toward the ceiling. And if the sensor fails, any CO-producing abnormality experienced by the fireplace will continue unnoticed and potentially harm building occupants.

Massachusetts, California, and a number of other states in the U.S., as well as Canada and other countries, have outlawed ventless gas fireplaces due to the aforementioned safety concerns. Many individual municipalities, too, have outlawed these appliances in states where they are otherwise legal. Advisements against the use of these appliances have been issued by various watchdog groups, such as the American Lung Association, the Centers for Disease Control, the Environmental Protection Agency, and even the Mayo Clinic. In particular, these organizations warn against exposure of individuals who are particularly vulnerable to CO, namely, the elderly, pregnant women, small children, those with pre-existing cardiovascular difficulties, and small pets. To be fair, though, there have been no documented cases of fatalities caused by ODS-equipped ventless fireplaces, according to the U.S. Consumer Product Safety Commission.

Watch for These Issues

To help ensure your ventless fireplace is operating safely, watch for these issues:

  • a gas leak. During production, installation or servicing, a leak can be created;
  • plugged burner ports. The contractor may accidentally plug the burner ports while spreading ceramic tile over the burners, or they may be painted over at the factory. The resulting unbalanced burn will create excessive carbon monoxide;
  • a clogged burner. Dust, carpet lint and pet hair can gradually choke off the fireplace’s air supply, leading to incomplete combustion and high amounts of CO that are vented into the living space;
  • high gas-input rate. Excessive CO ventilation or overheating of the unit will result from firing the gas higher than the input rate set by the manufacturer’s specifications. This can be caused by high gas-supply pressure, an incorrect orifice drill size done at the factory, or if the installer gives the customer’s unit a larger flame for aesthetic reasons;
  • the fireplace is oversized for the square footage of the area to be heated.
  • a cracked burner. The gas burner may develop a crack over time and function erratically, producing high levels of CO;
  • the fireplace contains items other than the artificial logs designed for the unit. Problems caused by the incineration of firewood or other flammable items will be immediate and extreme. A more likely and less obvious hazard is created by adding pebbles, lava rocks, and other non-combustible aesthetic touches to the fireplace, as their exposure to flames will cause an unsafe rise in levels of CO; and
  • a missing or defective ODS. As these components may fail, it is advisable to install a CO detector near a ventless fireplace and, ideally, in other rooms, as well.

Summing Up

In summary, ventless gas fireplaces, while very effective at heating an area of the home, have some issues associated with them that should be carefully considered by a homeowner. If you do choose to stick with your ventless fireplace, then be sure to install carbon monoxide detectors in the home and keep one window cracked open while you are using the fireplace.

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