Q:- Are you prejudiced against vent-free gas stoves or fireplaces because you're a Chimney Sweep and they don't need chimneys, or what?

A:- Vent-free gas stoves, gas logs and fireplaces are a very controversial subject. Debates involving scientists, the gas industry, code officials, and manufacturers are taking place in every corner of North America.

Rising sales of these low cost, ventless gas heaters will continue to drive this debate and ultimately resulting regulation. The controversy most recently involves regulatory agencies in California and New York, the American National Standards Institute and a subcommittee of International Approval Services.

Currently, eight states and eight Canadian provinces have outlawed ventless gas heating appliances altogether.

Washington State has taken a hard look at indoor air quality in recent years, and passed legislation designed to make the breathing environment in our homes healthier. One of the issues this legislation addresses relates to wood, gas and oil-burning heaters.

Studies have revealed that people who have these combustion-containing appliances in their homes live in an oxygen deprived environment all Winter. This has been linked to a number of health problems, including an irreversible lowering of white blood cell count.

Today, all new heating appliance and fireplace installations are required by Washington state law to draw their combustion air from outside the home. Washington State has yet to adopt a policy regarding vent-free appliances, which not only take their combustion air directly from the home, but vent gas exhaust into the breathing space: however, popular opinion seems to be that vent-free appliances will be banned here.

We subscribe to several internet hearth product discussion groups, and have followed the vent-free debate closely for some time now. We finally decided not to sell vent-free gas appliances, for several reasons:

(1) Aside from the unpleasant exhaust odor and the possibility of coating your entire house with black carbon deposits when they go out of adjustment, vent-free appliances are considered by many medical professionals to be a health hazard.

Indoor Air Quality scientists have warned that these heaters produce enough pollutants to make building occupants sick. There have been cases involving symptoms associated with low level carbon monoxide poisoning in homes where vent-free gas appliances are used.

Along with CO gases, gas consumption produces nitrogen dioxide: Proponents of vent free gas appliances recommend an allowable indoor nitrogen dioxide concentration of 0.5ppm, yet international, federal, and state agencies have reported that a concentration of only half that amount (0.25ppm nitrogen dioxide) will quickly result in unacceptable indoor air quality in climates with more than 2000 heating degree-days (Chicago, Washington, D.C., Seattle, Santa Barbara, etc.).

(2) Sizing vent-free heaters correctly for the amount of ventilation in the home and for the local climate is an important element in safe operation. The problem with sizing guidelines is that they are difficult to follow, since most installers don't have the necessary air infiltration and ventilation information. In addition, air quality officials have no way to monitor or control the maximum time these heaters are in use every day.

(3) Vent-free gas appliances not only burn up oxygen and dump poisonous exhaust into the home breathing space, but can also create an uncomfortably humid indoor environment. A 40,000 BTU vent-free fireplace will exhaust a GALLON of water vapor into the house EVERY TWO AND A HALF HOURS: disgruntled hearth product dealers who have sold vent-free appliances report customer complaints of dampness, mildew, mold, and peeling wallpaper.

(4) Manufacturers of vent-free appliances include a statement in the owner's manual requiring that a nearby window must be opened whenever the appliance is lit. Their claims of 90+ percent heating efficiency don't take into account the fact that the homeowner is required to open a window to the outdoor cold whenever the fire is going.

To read about how much CO2 a vent-free fireplace exhausts into the breathing space, click here.

To read about a recent study of the effects of long-term exposure to CO gases, click here.

To read postings from vent-free gas exhaust exposure victims, click here.

To read a posting about vent-free gas appliances from an indoor air quality scientist, click here.

To read exerpts from a recent Consumer Reports article about vent-free fireplaces, click here.

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