The Hidden Danger of Creosote Build-Up During the Burning Season

Despite the brutally cold weather, winter in The MKE is a festive time of year. In addition to shopping at the brightly decorated malls, there are numerous family-friendly outdoor activities in this winter wonderland, such as skiing, snowboarding, and ice skating. To stay warm and cozy during these frigid months, many Wisconsinites enjoy a roaring wood fire. Unfortunately, the hidden danger of creosote build-up often lies in wait in the chimney, frequently unleashing its destructive power during the burning season.

What is Creosote and Why is it so Dangerous?

Creosote is a dark, tarry substance that results from the incomplete combustion of wood. The smoke produced contains unburned particles, gases, and moisture. As this smoke rises, it cools and condenses on the interior walls of the flue, leading to the accumulation of creosote. This build-up can be a serious fire hazard if not removed. It is solid fuel waiting for a spark. Once enough build-up is present—sometimes as little as 1/8 to 1/4 inch—a stray ember, high heat of a wood fire, or even a lightning strike during a storm, can ignite it, causing a chimney fire.

Alarmingly, hidden creosote is the number one cause of chimney fires in the Milwaukee area. Just recently, a local restaurant in Brookfield closed temporarily after a chimney fire, likely fueled by creosote, spread to the roof, causing over $100,000 in property damage. This incident serves as a stark reminder of the hidden danger of creosote build-up.

 

The Three Stages of Creosote

There are three stages of creosote. Each stage is more volatile than the last.

Stage 1

A light, dusty, flaky soot that is easily brushed away with regular sweeping.

Stage 2

Soot evolves into crunchy flakes that become sticky like tar and are flammable.

Stage 3 (Fire Hazard)

The sticky tar hardens into a thick, dark glaze. It is incredibly dense, highly flammable, and difficult to remove without specialized tools and chemicals.

 

Watching for the Signs of Creosote Build-Up

According to the Chimney Safety Institute of America (CSIA), most chimney fires are small and go unnoticed. Watch for signs such as persistent odors or black build-up, and schedule a professional inspection promptly to prevent dangerous fires.

• A strong, persistent odor coming from your fireplace or stove, similar to an unpleasant barbecue or burning tar.
• Heavy, dark smoke is going out of the chimney or pouring out of the fireplace.
• Difficulty starting or maintaining a fire, or fires that don’t burn as efficiently as they used to.
• Visible black, tarry, or flaky build-up inside your chimney flue or around the damper.
• A loud, roaring, or freight train sound often signals a chimney fire in progress.

How to Prevent Chimney Fires

The good news is that chimney fires are preventable with clean-burning practices and annual chimney inspections and sweeping.

Annual Chimney Inspection and Cleaning

The National Fire Protection Association (NFPA) recommends that all chimneys, fireplaces, and vents be inspected by a qualified professional at least once a year. Your professional chimney sweep will inspect for damage and remove any dangerous creosote and soot.

Burn Only Seasoned Wood

Use hardwood (such as oak or maple) that has been split and dried for at least 6 months. Dry wood has a moisture content below 20% and burns hotter and cleaner, producing far less smoke and creosote. Never burn green wood, trash, cardboard, or treated lumber.

Maintain Proper Airflow

Ensure your damper is fully open during a fire. Good airflow provides the oxygen needed for a hot, complete burn, helping move combustion byproducts out of the chimney quickly.

Burn Hot, Not Slow

A hot fire creates a hotter flue, preventing smoke from cooling and condensing and reducing creosote build-up.

Chimney Cleaning & Creosote Removal Near Me

Do you know what’s in your chimney? Whether you have a burning fireplace, stove, or insert, a professional inspection and cleaning to remove hidden creosote is essential to reduce the risk of fire and carbon monoxide poisoning during the burning season. Smokestacks is proud to be the leading chimney professional serving the Milwaukee Metro area, including West Allis, Brookfield, Oak Creek, and Wauwatosa. Beat the winter rush—call Smokestacks today to schedule your chimney inspection ahead of the burning season.