Can A Flue Catch Fire? (Causes And How To Prevent It)

The last thing you want is a part of your home catching fire. Flues are used to exhaust fumes and smoke from your fireplace. Since they’re so near to actual flames, you might wonder, can a flue catch fire?

A flue can catch fire when it isn’t properly maintained. Over time, creosote and soot build up inside the flue. When the temperature becomes hot enough inside the flue, the buildup becomes combustible. Creosote will unavoidably build up inside a flue. However, you can slow down the buildup and regularly clean the flue to prevent fires.

Maintaining the fireplace and chimney is your best method of preventing fire. The flue, the part of the chimney that exhausts smoke, is what becomes coated in creosote, which is where chimney fires begin. How does this happen? How can it be prevented? This guide will explain all that and more.

Can A Flue Catch Fire?

A flue can catch fire if there’s too much creosote build-up. Creosote is a combustible substance that accumulates inside the flue. Creosote is a by-product of smoke, flames, and ash and can easily combust, setting the flue on fire.

Home fires happen for a variety of reasons, but improperly cleaned chimneys are the main culprit. According to the National Fire Protection Association (NFPA), one in seven house fires were caused by heating appliances (including fireplaces and chimneys) between 2014–2018.

A maintained flue isn’t likely to catch fire. This is because the materials used to make a flue are resistant to heat and flames. A flue is made from metal or clay liners with refractory mortar. Although both are heat and flame resistant, they can still catch fire if they aren’t cleaned.

Below is a table briefly explaining the differences between a metal flue and a clay flue.


What Causes A Flue Fire?

Creosote is the main cause of flue fires. Although creosote is a regular byproduct of your fireplace, it becomes an issue when it isn’t regularly cleaned off. A chimney that isn’t cleaned is at high risk of catching fire, as creosote is highly combustible.

Creosote is made of wood oils released during burning, smoke, and moisture in the chimney. This combination adheres to the sides of the flue, and over time, the creosote builds up into a tar-like substance. As this substance layers on the sides of the flue, it becomes flammable with high heat.

Creosote is also highly combustible, so you don’t need that much eat for it to catch fire.

How Do I Know If I Have A Flue Fire?

A flue fire is sometimes described as producing a popping noise and a hot smell. Usually, thick smoke can be seen coming out of the top of the chimney. A flue fire can go undetected the first time, but the flue fire wears down the flue lining and will be more dangerous during subsequent fires.

The first time that a flue fire happens may go unnoticed by the homeowner because it may be a slow-burning fire or a fire occurring in one spot of the flue.

You might have previously had a flue fire if you notice cracks in the flue or on the masonry outside of the chimney. Unfortunately, if this goes untreated, the next time, the fire may not stay contained in the flue and spread through the cracks to other parts of the home. This can lead to a damaging or lethal home fire.

Some ways to tell if your flue is on fire is to watch for:

  • Flames or flaming particles coming out of the top of your chimney
  • Loud popping noises
  • Roaring noises
  • Strong hot smell
  • Thick smoke

Anytime you see any sort of flame outside the chimney (either through a crack in the masonry or from the top), then you likely have a chimney fire. You should immediately get out of the house and call 911 for help.

How Do I Prevent A Flue Fire?

Regular cleaning, inspection, and repairs are preventative measures to avoid flue fires. Regular upkeep minimizes the creosote build-up, which minimizes the risk of combustion and the flue catching fire.

Since flue fires often start undetected, it’s important to stay up to date with regular inspections and cleanings to check on the flue’s condition. As a good rule, a chimney should be inspected and cleaned annually. During this time, the professional should look for signs of excessive creosote buildup and any wear on the flue.

The inspector can also alert you of any repairs or maintenance that needs to be done. Staying up to date on repairs will help keep the flue in good condition and avoid promoting creosote buildup.

How Can I Prevent Creosote Build-Up?

Since moisture and smoke promote creosote buildup, using treated or seasoned logs and maintaining proper airflow to the fire will help slow down the buildup. Burn a hot, clean fire and keep good airflow to minimize moisture in the flue.

Here are five tips to help reduce creosote buildup:

  1. Use seasoned logs. Dried out logs burn cleaner and produce less smoke and will therefore produce less creosote buildup.
  2. Airflow. Improve the airflow to your fire by fully opening the damper. Good airflow to the fire means it will burn more efficiently and produce less smoke.
  3. Avoid artificial logs. Artificial logs produce more byproducts than regular logs and can add to creosote buildup.
  4. Burn hot. Positioning the logs in your fire to allow for good airflow means that the fire will burn hotter. Using a fireplace grate will help to improve the airflow.
  5. Schedule your cleaning. Some creosote buildup is unavoidable, so be consistent in scheduling your regular cleaning and inspection.

When Should I Schedule A Chimney Cleaning?

Generally, a fireplace should be cleaned and inspected annually. Alternatively, if you can see a substantial amount of creosote buildup that’s greater than 1/8th of an inch thick, then it’s time to schedule a cleaning.

Creosote changes over time as the layers build up on top of each other. When it first begins, it will be a black flakey substance that’s easily removed. As it continues to build up, it will turn into a tar-like substance. The sooner it’s removed, the easier it will be to get your flue properly cleaned.

Dan Westfield

Hi everyone! My name is Dan and I currently have two fireplaces, a wood-burning and a gas one. I cannot live without them and love to share my passion with you all!

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