Fireplaces and Indoor Air Quality

Jan 6, 2020

It’s wintertime!  I don’t know about you, but in my family, a big part of the season usually involves gathering around the old fireplace and enjoying a crackling fire.  That’s why today I want to talk about potential hazards of fireplaces and indoor air quality.

Wood or Gas Fireplaces?

First off, we need to emphasize that there are two different types of fireplaces in the typical home: wood-burning and gas.  It’s pretty straightforward which is which. A wood-burning fireplace relies on wood as the fuel for the fire. A gas-burning fireplace relies on a gas line to ignite and provide the picturesque flame.  

Indoor Pollution

But in the world of indoor air quality, not all fireplaces were created equal.  Wood burning fireplaces are the bigger culprit for indoor air problems. Gas fireplaces can provide a cleaner-burning environment, generally speaking.  Wood burning fireplaces release far more pollutants than gas. The major reason for this is wood smoke. In fact, the EPA reports “when wood isn’t burned completely, the smoke it produces contains fine particles (also called particle pollution, particulate matter, or PM2.5), along with carbon monoxide and toxic air pollutants including benzene, formaldehyde, acrolein, and polycyclic aromatic hydrocarbons, and others.

Negative Pressure

Another danger from some fireplaces involves ventilation.  With a chimney flue, the fire creates negative pressurization that will suck indoor air up into the chimney.  This is not an efficient method of heating a home (I know this first-hand). This negative pressure can also have the unintended consequence of pulling higher levels of radon into your home.  I have been able to measure radon in my residence and have observed that the levels literally doubled during the time that I ran my wood burning fireplace.    

Ventless or Dangerous Fireplace?

A gas fireplace can also have its share of issues with ventilation.  This can occur with a “ventless” or “vent-free” fireplace. This is where a fireplace doesn’t have a chimney– combusted air inside the fireplace is sent directly out into the occupied space.  Unfortunately, it will also send pollutants into the living area. This can include lots of humidity, carbon dioxide, nitrogen dioxide, and some small amount of the dangerous gas of carbon monoxide. Personally, I think that the dangers of vent-free fireplaces far outweigh whatever benefits you may receive.  

Whatever type of fireplace you have, it is important to have a vented system that allows for the pollutants to properly exit to the outdoors.  

A Better Way

In fact, a superior option would be to invest in a sealed-combustion fireplace. This system uses a dedicated outdoor air intake and exhaust ducts to eliminate the combustion process affecting the indoor air environment.  This is considered much safer. Unlike many fireplaces, it does not create negative pressure that pulls indoor heat through the chimney and is also considered much more heat efficient. 

Steps to fully enjoy your fireplace:

  • It is always important to make sure the flue is open when burning a fire.
  • Make sure that the chimney is warm before starting a large fire. This helps ensure that the stack effect will draw the combustion gases out.
  • Purchase a carbon monoxide detector for the room with the fireplace.
  • If using a wood-burning fireplace, consider purchasing an air purifier.
  • Have your chimney and fireplace checked on an annual basis by a professional.
  • Use the proper fuels (i.e. properly dried wood for a wood-burning fireplace).