Traditional fireplaces are usually not counted as a heat source, because most of the heat goes up the chimney and they can actually suck warm air out of the house.
A quick look online reveals hearth sellers boasting of the “appearance, feel, and smell of wood burning in an open fireplace.” But they don’t mention the health risks from the and toxins, benzene and other VOCs, that a fireplace emits.
Fireplaces not only contribute substantially to outdoor levels of pollution, but they have significant impacts on indoor air quality as well. A recent , for example, concluded that people in a living room with an open fireplace are exposed to high levels of indoor pollution, with particles in a size range that “will be deposited in bronchioles and alveoli with great detriment to health.”
Another similarly found “extremely high” indoor particle exposure values from open fireplaces. The researchers concluded that the lifetime increased lung cancer risk from being exposed to a wood-burning fireplace in the home is “significantly larger than the EPA acceptable lifetime risk.”
As a side note, there can be other dangers from having a fireplace as well — mainly, children, pets and the home itself can be harmed by escaping flames and sparks. In light of the extra fire risk, a home owner with a working fireplace might be required to buy extra insurance coverage.
Masonry heaters are most common in Europe. They are usually custom-built in place and consist of an enclosed firebox and numerous heat exchange channels. They are built of brick or tile and look like an enclosed fireplace. They are meant to work by burning wood rapidly and slowly releasing stored heat throughout the day.
They are sometimes promoted as a lower-emitting option than a standard open fireplace. However, studies such as this one and have shown that, just as with other forms of wood heating, emissions can vary greatly depending upon how they are operated. As the authors of the latter study point out, “a restriction of air supply and too large fuel batches, which are the common operational errors in log-wood heating,” cause large increases in particle and gaseous emissions.