Creosote: How to better understand it and reduce its buildup?

If you own a fireplace or a wood burning appliance, you‘ve most likely been strongly advised to have your chimney cleaned annually,by a certified chimney sweeper,in order to remove creosote buildup. But do you actually know what creosote is all about and why is it so crucial to get rid of it? If not, this might encourage you to pay special attention to this very necessary task.

What is creosote?

Creosote is the leading cause of chimney fires. It is a smelly corrosive and highly flammable material that is produced by combustion gases that emanate from burning wood. When the temperature inside the flue decreases below 250 degrees Fahrenheit, the gases condense in your chimney, creating buildup along the lining of the pipe. Since flue temperature often drops below this thresholds, creosote regularly builds up.

Extreme heat and burning embers drifting up the chimney can ignite creosote buildup. If there is an extensive amount of creosote, the fire could spread to your home. This is why annual chimney cleaning is so essential.

Stages of creosote buildup

Creosote gets created in stages. Each stage brings it closer to a greater danger, as it becomes thicker and harder to remove.

Stage 1:Creosote is soft and flaky like soot. It can easily be removed with a simple chimney brush.

Stage 2:It condenses into a hard, shiny and scaly substance that clings to the flue lining like tar. Though it may look flaky, it cannot be brushed away easily. The most effective way to remove stage 2 creosote is by using a rotary loop; a stainless-steel cable fixed to a hub that is put on special metal rods, turned by a powerful drill.

Stage 3:The chimney sweeper’s main goal is to prevent creosote buildup from reaching this stage since it then represents a sticky and highly concentrated fuel. This tar-like substance hardens along the chimney lining and thickens as the creosote condenses. The coarser and harder it becomes, the more challenging it is to remove. At this stage, chemical removers can sometimes be used. A rotary head mounted with chains could also be effective when it has hardened but is not sticky; however that particular solution is not recommended for clay or ceramic chimney linings since the process can also dislodge broken pieces. In most cases, the best option is to remove the flue lining and replace it altogether.

Without proper equipment and training, it is much-preferred to leave creosote removal to professionals.

How to minimize creosote buildup

With a wood burning fireplace or a stove, it is impossible to completely eliminate creosote buildup but there are ways to minimize and prevent it from reaching stage 2 or 3 while waiting your next visit from the sweeper.

Only burn dry, seasoned firewood

You can measure wood humidity with a moisture meterYour wood must have dried for at least 6 to 12 months and must have reached a humidity level of less than 20%. Newer wood contains too much moisture and produces more smoke while burning.And it is this smoke that turns to creosote. The drier the wood, the less it smokes, thus producing less creosote! The best way to determine if the moister of your wood is optimal for creosote prevention is to buy a moisture meter at your local hearth retail store.

Before testing your wood, split your log in half. The outside might seem perfectly dry but the inside can still hold too much moisture.

Another advantage to this procedure is the fact that moist wood also decreases total heat output, since a huge amount of energy is wasted in your fireplace on boiling and evaporating the water inside each log.

Insure your fire has sufficient air flow

Air is essential to any efficient fire. If your fireplace is equipped with glass doors, it is wise to keep them opened so your fire can breathe. This will insure burning at higher temperatures and elimination of a large quantity of combustion gases.

Properly lay-out your logs for more efficiency

The way the firewood is laid-out affects the fire overall performance. Pack it tightly but leave small gaps in between to allow airflow. Make sure not to close the fireplace doors (ceramic glass) or to restrict air flow adjustments too soon, before the fire gets hot enough. It may not be if it starts to smolder or looks like it might die out.

Below is a list of fireplace and grill stores that service Virginia (VA)

Mechanicsville, VA

Hearth & Home Shoppe
8151 Mechanicsville Tpk
Mechanicsville, VA 23111

Visit Store Page

Roanoke, VA

Dixie Building Products Inc.
3342 Melrose Ave NW
Roanoke, VA 24017

For more information, contact your local fireplace and grill store..

2 Responses

  1. I like your article, I ran my wood buring stove for 4 years always cleaning with wire chimmeny brush each year never had a problem. This year i got alot of smoke back into the house, long story short took the pipe off my wood burning stove and was amazed at the amount of build up in my pipe looked like a cave with lots of cone shapes from the top and bottom. One thing i did differant this year is once the fire was going good i would turn it down into the 250 range before going to bed and then reduce the air intake alot so it would put out heat all night and have ambers in the morning. Would this cause such a fast build up of Creosote?
    • Dominique Page
      Hello Michael Thanks for your comment. Running at lower temperatures increases the risk of incomplete combustion. But the greatest factor is the quality of the firewood we burn. If it isn't 'seasoned' properly, we need to run at higher temperature to keep the chimney system clean. When you say 250F temperature, is it using a a magnet thermometer on a single wall stove pipe? If so, you might want to run closer to 300F. Good work on cleaning your chimney!!! Dominique

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