Wood Stoves, Fireplaces, and the Danger of Pyrolysis

As one of the oldest cities in Pennsylvania, many Allentown area residents still rely on wood stoves and fireplaces for home heating and an ambient atmosphere. However, firebox or flue damage from neglect or improper installation of newer heating appliances pose a hidden danger that most people have probably never heard of. It’s called pyrolysis. In this article, we’ll discuss the danger of pyrolysis to wood-burning fireplaces and stoves.

What is Pyrolysis?

Pyrolysis is the thermal decomposition of organic matter in the absence of oxygen. It occurs in solid-fuel appliances when wood heat rises to high temperatures without enough oxygen to support complete combustion, such as heat transfer to combustible materials that reignites the wood logs in the stove or fireplace. Pyrolysis is a high-heat event that causes the wood to break down into a complex mixture of gases, tar, and particulate matter. It can also lead to a fire burning out of control, resulting in extensive property damage.

Why is Pyrolysis Dangerous?

Pyrolysis poses several significant risks to your family and property:

Increased Fire Risk 

First, the accumulation of creosote deposits and flue liner cracks or other damage increases the risk of chimney fires. If a fire starts in the fireplace or chimney, it can quickly spread to the surrounding structure.

Creosote Buildup

Second, the tar produced during pyrolysis often condenses and adheres to the inside of the flue, forming creosote residue. As it continues to accumulate, this sticky, tarry substance can restrict air flow, reduce efficiency, and increase the risk of fires.

Flue Damage

Third, the corrosive gases and particulate matter released during pyrolysis can damage the flue liner over time. This can lead to structural weakness in the chimney and create a pathway for smoke and toxic carbon monoxide exhaust to enter your living space, reducing indoor air quality.

Signs of Pyrolysis in Your Fireplace or Wood Stove

Is there a hidden danger hiding in plain sight? There are several signs to look for that could indicate that pyrolysis is occurring in your wood-burning appliance:

• Smoky Fires: If you notice more smoke than usual coming from your chimney, it could be a sign of incomplete combustion caused by pyrolysis.
• Creosote Buildup: Those dark, sooty deposits on the interior masonry walls, chimney cap, throat damper, and flue liner are creosote and must be removed safely.
• Incomplete Combustion: If wood is not burning completely, leaving a lot of unburned residues or stains, it’s a sign of pyrolysis.
• Difficulty Starting Fires: Are you having trouble starting fires or maintaining a consistent flame? It could be from restricted airflow caused by creosote buildup, a symptom of pyrolysis.
• Burning Odor: A burning smell may indicate pyrolysis, especially when the appliance is not in use.

What to Do?

If you suspect that pyrolysis is occurring in your wood-burning appliance, it’s important to take immediate action:

1. Avoid Using the Appliance: Only use the fireplace or stove once a certified chimney professional completes an inspection and resolves the issue.
2. Schedule a Chimney Inspection: Contact a chimney professional to examine the condition of your chimney, fireplace, or stove, remove any creosote buildup, and identify any underlying issues.
3. Make Necessary Repairs: Follow the chimney sweep’s recommendations to repair any damage to prevent future pyrolysis events.

How to prevent Pyrolysis in Solid Fuel Appliances?

• Improve Ventilation: Ensure your home has adequate ventilation to provide enough oxygen for complete combustion.
• Use Seasoned Hardwood Logs: Burning dry, seasoned hardwood logs, like Birch or White Oak, with a low moisture content can help prevent pyrolysis.
• Maintain Clearance: Ensure that combustible materials like rugs, carpeting, furnishings, and other objects are at least three feet away from a combustible source, like your wood-burning fireplace or stove. Trim tree limbs so they are not touching the roof or chimney.
• Regular Maintenance: Have your chimney inspected and cleaned regularly to prevent creosote buildup and other problems.

Contact Wells & Sons for Expert Fireplace Repairs

If you notice signs of pyrolysis or other damage to your wood stove or firebox, call Wells & Sons Chimney and Fireplace Service now. We’re family-owned and operated and have 45 years of industry experience. Our certified technicians will conduct a thorough inspection and recommend the necessary repairs to restore the safety and elegance of your wood-burning heating appliances.

We proudly serve homeowners in Berwyn, Lansdale, Norristown, and the surrounding Lehigh Valley region. Contact us to book your appointment now.