Wood burners that have been heating with wood for years are familiar with the dangers of having excess amounts of creosote in a chimney flue. However, homeowners that are new to wood burning may not. So today we are going to take a look creosote, what it is, and how to prevent it building up.
What is Creosote?
Creosote is a gummy, foul smelling, corrosive, and extremely combustible substance that if no precautions are taken will coat the inside of everything that it passes through. By definition creosote is simply unburned wood particles and condensed flue gases which deposit on the inside of your chimney.
How Creosote Builds Up
Creosote forms in your chimney as the flue gases exit the fireplace or wood stove and draft upwards into the relatively cold flue where condensation occurs and begins to solidify. This results in a carbon based condensation that materializes inside the flue and becomes creosote.
As creosote builds on the chimneys interior it goes through stages becoming more and more of a hazard as it goes through each stage. All 3 stages of creosote can exist in one chimney and no matter if you have one or all three of the stages it is going to be highly combustible.
Dangers of a Chimney Fire
If the creosote is allowed to build up in sufficient quantities and ignite inside the chimney flue the result is a volcanic chimney fire the can eliminate or cause excessive damage to your home in just a matter of minutes.
Creosote buildup is also pretty sneaky. You may not even notice it at first but it tend s to feed on itself. As it builds up it is going to restrict the flow of the chimney or stovepipe causing the smoke to slow down on its way out of the chimney. This allows more time for that smoke to cool, forming more creosote thus further restricting the flow of your chimney, causing the cycle to continue and worsen. If you are not addressing the creosote buildup it can quickly build to a point where it is too dangerous to be taken care of by anyone other than a hired professional.
A chimney fire will occur when built up creosote deposits are ignited by extreme heat from the fireplace or wood stove. For this to occur it does require that the creosote be subjected to high temperatures of over 1000 degrees or so. Though 1000 or more degrees does seem a bit extreme the following quote from the March 1990 Home and Hearth Magazine puts it into a good perspective, “Creosote buildup by itself or in combination with other factors was involved in 92% of chimney fires reported in a study commissioned by the Wood Heating Alliance.” A buildup of as little as 1/8” to ¼” of creosote is sufficient to create a fire hazard.
How to Prevent Creosote Build-Up
The best thing to do to reduce your risk of excessive creosote build-up is prevention. There are a few different things that you can do to help prevent creosote build-up.
First things first, the wood that you burn has a lot to do with the amount of creosote that you are going to see in your chimney. All firewood contains water to some degree but how much it contains is what is important. All of the water contained in the wood as you burn it is going to evaporate into water vapor as the wood burns. The water vapor then enters your chimney at approximate temperatures of 212 degrees F. The water vapor will be considerably cooler than the condensing point of creosote gases which is 250 degrees F.
As that water vapor enters your chimney it is going to cool the chimney. The water vapor then mixes with the gases in the chimney and condense. That is how creosote is formed. This is true whether you burn hardwoods or softwoods. The moisture content is really all that matters. It is important that when you choose your firewood you check your firewood, before you start burning it, to ensure that it is properly seasoned with a moisture content that is between 15-20% for optimal burning.
Why Chimney Flue Temps are Important
Another way to prevent the dangers of creosote buildup is to keep the chimneys temperature above 250 degrees Fahrenheit all the way up. The warmer the walls of the chimney the less the creosote can adhere to them. The temperature of your stack is also affected by the size and location of the chimney. If the chimney is on an exterior wall as opposed to an interior wall it will constantly be subject to outside cooling effects. If the chimney is over sized it is also going to require more heat to keep those surface walls warm due to the increased mass. With this thought in mind you can see how a very large chimney that was never really warmed up would have the potential to have excessive creosote deposits.
Burning wood whether in a fireplace or a wood burning appliance offers many advantages to the homeowner including the allure of heating with wood, the joys of stoking the fireplace, and tending to the demands of your fire. By taking a couple of steps to keep your fireplace clean from creosote buildup you will enjoy all of the benefits of natural wood fires without the risks of an unnecessary chimney fire.
I hope that you found this information from NorthlineExpress.com helpful. If you still have questions about creosote, the dangers, or products for removal please give our customer service department a call at 1-866-667-8454. Here at NorthlineExpress, home of the Buy and Try Satisfaction Guarantee, we are always happy to help.
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