Keys to reducing soot dangers in gas fireplaces
Improper placement of logs in a gas fireplace can create soot and other risks.
A fire has an innate ability to catch our attention. Uncontrolled fire is terrifying and deadly, but the controlled burning of wood at a campfire or in a fireplace creates an unmatched ambiance and warmth. For that reason, a common amenity in houses today is the gas log fireplace insert.
When not installed properly, these logs will generate soot particles that can leave the fireplace and travel throughout a house. If enough soot gets into the HVAC system, soot can be deposited in every room throughout the home. When logs create a lot of soot, it is usually noticeable immediately and quickly corrected. However, when the logs produce lesser amounts of soot that builds up so slowly, it is not as noticeable until you adjust a picture frame and see how dingy the wall has become.
Soot dangers
It can cost tens of thousands of dollars to clean soot from a home since soot removal is a specialized restoration service that typical homeowners cannot handle themselves. Where there is soot, there is also carbon monoxide, which can cause a host of physical ailments. Prolonged exposure to soot can unleash a range of breathing problems including asthma, bronchitis and respiratory infections.
Why does this happen? Remember that combustion is a chemical reaction at its roots. The clean or complete combustion you want in a furnace or stove results in that quintessential ‘blue’ flame. (Figure 1) In those applications, that is exactly the desired result: maximum efficiency and heat for heat transfer. However, if the fuel-to-air ratio is modified, you can bring some yellow to the party and have a gas flame appear more like the flames generated by a wood fire. Still, the yellow Bunsen burner doesn’t draw you to sit down to bask in its output, does it?
Hence, the gas log fireplace insert. At the heart of it, a typical gas log fireplace insert is a burner that has the proper fuel-to-air ratio for either natural gas or propane to produce the yellow flame similar to a wood fire. They also have ceramic ‘logs’ that are placed around the burner to further mimic the look of a wood fire.
The proper placement of the faux logs is critical to the safe operation of the fireplace. From the front, the logs give the appearance of a stack of wood. If you inspect the set from the top, however, the area around and above the burners is free from objects. If the logs are improperly placed or are knocked out of position and get in the way of the flame from the burner, then impingement occurs. The flame impinging on the ceramic log will cause soot to form.
Therefore, when installing a gas fireplace insert, follow the log placement instructions carefully! If there is no glass in between the logs and whatever room they are in, it’s also not a bad idea to check the log placement when doing annual maintenance on your fireplace insert.
Jennifer Morningstar, PE, CFEI, is president and senior consulting engineer of Warren Forensics. Her areas of emphasis include chemical release & exposure, OSHA process safety management, industrial accident investigation, fires & explosions, and scope of damage/cost to repair analyses. She is an OSHA-trained Process Hazard Analysis study leader and completed Root Cause Failure Analysis training to become an Incident Investigator. Contact her at jennifer@warrenforensics.com.
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