Ordinary gas fireplaces must be vented to the outside for safe operation. Ventless fireplaces are designed to produce less carbon monoxide, so they may be used without a vent. However, these devices can cause respiratory problems if they malfunction, or in the homes of people with existing respiratory problems.
Mold
The process of combustion produces moisture, even if the fuel is something as efficient as natural gas. Vented gas fireplaces move this moisture outside, but ventless fireplaces have nowhere to release it except into the home. Increased humidity in and around the fireplace can contribute to mold growth, especially in homes that already have high moisture levels. This mold may look like just a nuisance, but several species of mold can actually cause respiratory problems and aggravate allergies or asthma. Owners of ventless gas fireplaces should take care to control moisture and mold in the area of the fireplace using dehumidifiers, good ventilation and frequent cleaning.
Carbon Monoxide
Like all devices that burn fuel, ventless gas appliances produce carbon monoxide. They do burn more efficiently than conventional vented fireplaces, reducing the danger of carbon monoxide poisoning. According to the home improvement website Ask the Builder, ventless fireplaces also include carbon monoxide detectors that shut down the combustion process when levels of this gas get too high. However, these safety mechanisms aren't foolproof. If the carbon monoxide detector on a ventless fireplace stops working, it could release significant amounts of poisonous gas into the air. Ask the Builder recommends that owners of vented and ventless gas appliances consider installing a separate carbon monoxide detector as a safety measure.
Air Quality
Even when the fireplace is functioning correctly, it can degrade air quality. Ventless gas fireplaces rely on the oxygen in indoor air to burn their fuel. Over time, they can deplete oxygen levels in the home, while releasing combustion byproducts such as carbon dioxide, nitrogen dioxide and water vapor, all of which reduce indoor air quality. People with existing respiratory conditions may find it more difficult to breathe freely when a ventless fireplace is in use. Whenever possible, install ventless gas fireplaces in well -entilated areas of the home to improve air quality.
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