For many years in this country is was
not possible to buy a heating appliance that did not have to be
vented to the outdoors but, ventless heaters are back and somewhere
around 7 million homes have them now. Good thing or bad thing? Well,
it's a little of both.
The recent boom in the use of ventless heaters and unvented gas fireplaces was made possible by a handy little device called an oxygen depletion sensor, or ODS. This little critter is part of the pilot light burner and will shut the heater off if the oxygen level in the room drops to roughly 18 percent. If the oxygen level in the room is dropping this means that the percentage of harmful fumes is rising. This safeguard protects you from the buildup of carbon monoxide, the stuff that can make you sick or kill you in a hurry. Therefore, we now have a product that's safe to use. Right?---In the short term, yes. But what about the long term?
If you are using a vent-free heater as a main source of heat in your home you are breathing the products of combustion that they put off every day, day in and day out. There are all kinds of different chemicals as well as gallons of water vapor put off by a burning flame. This can't be healthy. People that have asthma, allergies or any other kind of respiratory problem can be acutely affected over time. Because of the number of complaints of illness and the scientific communities concern, many states in this country and many other countries including Canada and Britain have banned the use of these products.
So...... I guess we shouldn't use them. No, I'm not saying that. Use them as they were intended to be used. Got a family room that you want a little ambiance in? Use an unvented gas fireplace for a few hours a couple of times a week. No problem. Need a little heat in your workshop, garage or basement while you're tinkering around? They're great for that. (I have one in my basement that I use.) Vent-free appliances are also a great backup source of heat in case of a power outage. You can keep your house and pipes from freezing up because they require no electricity to work.
But understand this. Our bodies are made to use fresh air, so it's not a good idea to live in a chimney. If you use ventless heaters as the main heating source in your home that's what you're doing. Think about it.