Ventless gas logs have certain problems that differ from other types of gas logs. For example, common complaints include an overpowering scent, water vapor and carbon monoxide (CO) emissions. Yet, these appliances continue to increase in their popularity due to their efficient operation. There are ways you can enjoy the warmth of ventless gas logs and reduce experiencing the worst of some of the reported side effects.

...

Benefits

Ventless gas logs, unlike real wood and vented gas logs, do not require a chimney, so heat is efficiently contained within the house. For some, it is the preferred choice over natural wood and their venting gas log counterparts. Another benefit of the vent-free type, is the lack of flying sparks that could damage furniture placed near the gas log appliance. You also do not have to deal with ash residue that comes from the burnt-out flames of real wood.

Strong Odor

Off-gassing is a common problem associated with ventless gas logs. This happens because odors stay trapped in in the air after flames are produced. Chemical changes occur after the logs burn when the air comes in contact with carpet, furniture and common household items like bleach and paint. Without a chimney as an exiting source for these odors, the smells can be in some cases, overwhelming. Since the logs need oxygen from the air in order to produce flames, this occurrence is hard, but not impossible to avoid.

Water Vapor and Mold

The burning gas from ventless logs produces water vapor. The vapor can accumulate over a period of time and create an environment for mold growth. Excessive mold can trigger allergies, cause sickness or prolong it and therefore, affect your comfort level within your home.

Carbon Monoxide Emissions

Contrary to what some may believe, even small amounts of CO exposure can be damaging to humans. Dizziness, headaches, nausea and even permanent brain damage can result from long-term, low-level CO exposure. Logs are considered safe for home installation if the set tested at 9 ppm (9 per million) or below.

Generally, newer homes are built with tighter insulation. Cool air stays inside during the summer months and warm air stays put during the winter months. Since everything is kept in, exposure to CO has become a major concern as negative gases can result from the backed-up air pressure.

Prevention/Solutions

Although, there are some problems with ventless gas logs, there are tips to lesson the side effects. First, if you are looking to make a purchase soon, look at the newer models out there. Older ventless models generally have higher CO emissions. Second, read the owner's manual regarding the proper way to use the appliance before investing in it. Third, have your house checked for negative pressure and then if necessary, invest in a whole house ventilator to combat it. Negative pressure can occur when back-up gases pile up from the gas logs, hot water heaters and furnaces. This is known to happen in newer homes due to their tight insulation. Fourth, place the appliance in an large enough open space so the air will flow. Don't place the ventless gas log set in a small room or inside a manufactured fireplace because the potential for fire is too great. Lastly, if you already own a ventless gas log set, conduct research to see if it is outdated and if so, consider replacing it with a newer model for safety reasons.