Inhabitat and Mocoloco recently covered vent-free fireplaces like the Schulte unit shown here and we have thought that some of them are pretty slick design items. The Schulte appears to be fuelled by "a liquid that is smoke and emission free" but whenever you burn something there is a product of combustion; even hydrogen produces water. Most of the European liquid fueled systems use alcohol gel, , and some claim that the only product of combustion is water vapour. We asked resident expert John Laumer who wrote: " This is probably what we call "Sterno," a methanol based fuel. The gel prevents spillage. It probably also contains a bittering and nauseating agent that absolutely precludes people and most pets from drinking it.....because methanol is the shortest alcohol molecule it produces very little C02 compared to any other hydrocarbon liquid. Much of the liberated energy is from hydrogen combustion." In modern tight houses, the water vapour could lead to a condensation and possible mould problem, but if you have a heat recovery ventilator that should be OK. However in the end, like cheap candles, why put anything into the air you breathe?
The other kind of indoor fireplace we have shown is the catalytic gas fireplace, which burns at a very high temperature with "a ceramic catalyst that cleans the products of combustion, removing hydrocarbons and allowing the fireplace to emit absolutely no carbon monoxide. Vent-free fireplaces also employ an Oxygen Depletion Sensor (ODS). This device measures the amount of oxygen in a room-20.9 percent being normal. If the oxygen level drops too far, the ODS shuts off the unit." Some even claim to improve air quality, which we questioned in a recent post admiring the fireplace shown.
The American Lung Association came out against them, and many governments ban them. In response, The Vent-Free Gas Products Alliance came out swinging, with research saying "vent-free gas heating products performed well within nationally recognized guidelines for indoor air quality. This research proves that vent-free gas heating products meet applicable emissions requirements even when used over extended time periods, among sensitive populations, and with units whose maximum heat output exceeds the requirements of the space." and "for the vast majority of homes in the U.S. (99%), vent-free gas heating product DO NOT generate enough water vapor to raise indoor humidity levels high enough to foster mod growth.", all of which sound a bit like weasel words, without any explanation of what "applicable emissions requirements " and "nationally recognized guidelines for indoor air quality."
Others don't like them at all. A recent newspaper article looking at fireplaces said "Do not install a ventless or vent-free fireplace in your home. There's no prohibition against selling such devices, but you can't have them in your house — and for good reason. Children, the elderly and the infirm can be harmed by carbon monoxide before healthy adult males show any symptoms or CO-detecting devices kick in." They are not legal in Canada (according to our preliminary research) and we link here to a long article about their safety, or lack thereof.
In the end, we come down to the conclusion: Spend a bit more money and get a good vented gas fireplace or EPA approved vented stove. We breathe enough chemicals and carbon monoxide in our lives, we should not be doing it in our homes.