Traditional fireplaces are usually not counted as a heat source, since they 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 that a fireplace emits. , for example, found that fireplaces emit significant amounts of benzene and other VOCs.
The US EPA developed standards beginning in 2012 for certified fireplaces. Hearth sellers like to promote these newer fireplaces and fireplace inserts as “clean burning.” Assuming their emissions ratings, which are based on , are even accurate, a fireplace meeting these new guidelines might emit “as little,” according to the ads, as 4.4 grams of particulates an hour. For comparison, the exhaust from a modern passenger car .195 grams of PM2.5 per hour of driving at freeway speeds. You’d have to drive day and night for more than 3 solid days without stopping to create as much particle pollution as from using the best “clean burning” fireplace for 3.5 hours.
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.