How To Remove Creosote Buildup
What is Creosote?
Creosote is a flammable and corrosive substance that can build up on the walls of your fireplace and chimney. Creosote is formed when unburned wood particles, fly ash and other volatile gases combine as they exit the chimney. If there’s a poor draft, these unburned particles and gases can condense and build up on the walls of your chimney. Over time, these creosote or soot buildups can become a danger as they can potentially result in a chimney fire.
Causes of Chimney Creosote Problems
Smoke, or better termed, flue gas, is released by the initial fire, or primary combustion. Burning wood, no matter how it is done, releases pollutants in the form of gases and particulate matter. Flue gas, comprised of steam and vaporized but unburned carbon based byproducts (vaporized creosote). If smoke exiting the chimney is cooled to below 250 degrees Fahrenheit, the gases liquefy, combine, and solidify to form creosote. A flue too large for the woodburning appliance may increase the likelihood that creosote will build up. Restricted air supply, unseasoned or rain-logged wood, and cool surface flue temperatures also encourage creosote to build up.
Creosote Stages:
- Condensation: In an attempt to save fuel, many people reduce the amount of air entering the combustion chamber, causing the appliance to smolder. This has serious side effects. Smoke then cools as it rises in the chimney, not having enough heat energy to escape the stack. The flue gas then condenses on the inside of the chimney and the sap/resin turns into creosote.
- Liquidation: This sap/resin turns liquid and can seep into mortar joints or cracks in the flue tiles. The corrosive property held by creosote destroys masonry work and jeopardizes the life of your chimney.
- Solidification: As temperatures fall and rise within the chimney, causing the heating and cooling of the creosote. This quickly enables build-up, reducing the amount of space the flue gas has to exit the chimney and, in extreme cases, blocking the flue completely. This build up can look like tar and is frequently termed βtar build-up.β
- Friable State Creosote: When the solid creosote is burned, all volatile oils are removed leaving a residue that appears very similar to honeycomb which is crisp and easy to sweep from chimneys.
Creosote Glazing
Glaze is formed in the solidification stage and occurs when new layers of creosote are being added so quickly that the layers below it have no time to dry. These fresh layers then insulate previous deposits so it eventually solidifies creating the rock-like substance known as glaze.
How to Remove Creosote Glaze
To remove this hard-as-a-rock glaze, it must first be broken down chemically. The two best products to use are Anti-Creo-Soot (ACS) Liquid spray or ACS Powder. ACS in liquid form is a chimney creosote removal spray that can be applied directly onto the fire or used to pre-treat the wood before burning. The vapor goes up the flue and attaches to the glazed creosote and chemically modifies it, converting it into a harmless ash that can easily be swept out with a chimney sweep brush. ACS in powder form is a little bit more powerful. This powdered chimney creosote remover is applied to the chimney walls and up the flue. When you start a fire, the temperature needs to reach 300 degrees F. Once this happens, the ACS Powder causes the creosote to expand and contract at a different rate than the flue it’s attached to, causing it to peel away from the flue liner. Both of these products contain unique chemical catalysts that breaks down the creosote over time. They are the most powerful when used in combination. Use the ACS Powder for the first 2 weeks to break down the really heavy duty creosote. Then use the regular ACS liquid spray every time you have a fire. Give it 5-6 sprays each fire to reduce creosote buildup and keep your chimney creosote-free.
After you solve your creosote problem, it’s a good idea to check the rest of your chimney and make sure it’s in good shape. Keeping your bricks waterproofed and performing chimney crown repair if needed are essential steps to take to keep your chimney in proper repair.
Category: Chimney Creosote Problems
Subscribe
If you enjoyed this article, subscribe to receive more just like it.
I have a problem with creosote buildup in my wood-burning furnace. I have shared my problem with the manufacturer and they told me to contact your company for help. The creosote is inside the heat exchangers. What do you recommend?
Jimmy Moore
Lawrenceburg TN
Jimmy,
Hire a professional to come out and take a look at the apparatus. There should not be any creosote building up inside the heat exchangers; the only logical place for creosote buildup is up in the flue system itself. This problem needs to be addressed by a professional.
[...] they can identify needed chimney repairs. Special logs can be used that contain chemicals to reduce creosote buildup. One brand is named chimney sweeping log. Find these at neighborhood hardware stores.Much of roof [...]
We have a problem. We just moved into a house & it appears that the chimney is completely blocked with creosote. It looks like the previous tenants tried to use a chimney brush from the top causing the “honeycomb” creosote to fall and blocking the entire chimney about 6′ up from cleanout box. My husband has tried pounding a steel rod through to punch a hole in the dense creosote but nothing seems to be working. Do we have any options? Are there any chemicals that can work to dissolve the creosote without being burned? Obviously we can’t burn/use the woodstove until the smoke has somewhere to go. Any practical advice you can offer is greatly appreciated.
The tiles will probably have to be removed from this chimney flue system and an insulated stainless steel liner installed. If you are considering burning wood in this fireplace, it would be prudent to have the chimney properly lined. This is a radical situation that we don’t often see, and due to the severity of your buildup, my professional opinion is to have a professional come out to estimate the creosote and tile removal and installation of a chimney liner. Refer to professionals that are licensed by the National Chimney Sweep’s Guild, which you can check out on their webpage ncsg.org or the Chimney Safety Institute of America csia.org. Hope this helps! Burn safe and warm.
I have a 15 year old fireplace and chimney. I burn maybe 15-20 fires a year using seasoned wood. The damper is always wide open and I don’t
have any of the symptoms of a clogged flu. Never been cleaned. Am I
on thin ice?
about 10 years ago, I had a chimney fire in the flue of my wood burning fireplace insert. I was lucky in so far as I did have a couple of sticks of “Chimfex” to throw into the insert after I heard the roar and saw flames shooting out of the chimney stack (which lit up the cold winter night). Chimfex chokes out fire when thrown into an air-tite stove. My local fire department came quickly to crawl onto the roof and into the attic to determine that nothing had caught fire in the house structure, although the aluminum cap over the flue did melt in the fire-blast. I then contacted a professional to look at my setup, which I had gotten when I purchased the home a few years earlier. The metal flue from the fireplace insert only went about 4 feet up the chimney, then ended leaving the smoke and creosote to buildup on the interior of the chimney masonry… which it did for at least 4 years while I had lived there. He cleaned everything, then installed a double wall stainless liner, which he wrapped in a mineral wool blanket ( to help keep flue temps up and creosote buildup down) down the entire length of the masonry chimney. He also fabricated a connector from the round flue to the rectangle opening at the back of the insert. He capped the flue with a SS flue cap to keep out birds and such. The cost was nearly $2,000 10 years ago, but the thought of another chimney fire made me spend the money for peace of mind. Here I am 10 years later… I typically burn a really hot fire every 3 or 4 burns for at least an hour, ( I burn almost every day in the winter) and throw in one of those anti-creosote sticks that look like a flare into the fire every couple of weeks. Last November I had my chimney swept for only the second time in 10 years, and although it needed it, the buildup flaked off easily. In your situation, I highly recommend getting a good pro to look at your particular chimney and then spend the money to get it fixed correctly. A chimney fire is no fun at the least and life-changing at the most. I go to bed every night in the winter warm and content in the knowledge that I have done everything to keep my home from burning down that I can.
Great report on the Chimfex I hope every wood burner hears you loud and clear. I like the statement regarding the professional inspections and service work! It sounds to me like your getting away without a lot of sweeping. I would keep checking the flue pipe regularly and keep changing those batteries in the smoke detector and carbon monoxide detectors. That is what will wake you up at night if their is a problem.
Sounds like you’re burning safe and warm
Clay
You bet you are! National codes state inspection should be done yearly . 15 x 15 is 300 fires, and whether these are one night fires or three day fires plays a factor in the equation as well. My point is that I would at least inspect the chimney system once a year at a minimum or after each cord of wood burned. Get your ice skates on, or I would recommend getting off the ice.
Burn Safe and warm!
Clay
a chimney sweep service said i need to have my flue cleaned over two sessions by what they called a PSR Treatment. could you please explain this treatment / process
Alan,
I am not sure what that is? I would ask to see the manufacture information, I am sure that they will have a website you can look at. Read the contract before you sign. They should also give you a referral and if any a 800 number.
I have a wood add on my furnace my problem is creosote ran down my outside of my chimmey all over my vinyl siding how do you remove this
I feel that you are treating the symptoms and not the problem here. You first need to resolve the creosote problem and why there is a continuous buildup. Without seeing it I would guess it’s one of three things.
1) The cap is being clogged because the fire is being chocked down to much.
2) Second, it’s improperly sized off the back of the furnace. Code standards state that the venting size needs to be the same sq. inches off the back of the furnace unit all the way through the entire chimney. In other words you can’t mix sizes of pipe or chimney flue venting sizes.
3) Three your fire wood is unseasoned and is causing an excessive creosote issue.
After the creosote problem is resolved, I would go to a local hardware store or big box store and ask for a product that might work without damaging the vinyl siding. I would test small areas before you clean the whole vinyl wall, to make sure it will not damage it.
We had our chimney (fire place) swept the other day and at the end the fellow told us about other repairs that he would recommend doing. Some immediately (see below) and others in the coming 1-3 years (fixing the cap). One recommendation is to have our chimney chain whipped due to cresote buildup at the bottom of the flue. He said the top of flue was fine.
Last thing I want is a chimney fire, but from what I am reading about creosote (this site and others), most comments discuss using a catalyst to help break down the creosote and few mention chain whipping as a first option. I do have experience with fire places/wood stoves and understand the importance of buring hot fires and recognize that this past winter I did have some moist wood and the fires weren’t as hot as usual.
Additionally, there was something about the sweeper that made me feel like he was trying to up-sell me on other services (e.g. he can clean my dryer vent hose for $150!). I will obviously start using anti-cresosote sticks, but I would like to hear others’ thoughts on chain whipping.
Thanks, Bob
I also offer chain cleaning that is often referred to as Ro-clean or mechanical cleaning. This is process is completed with sections of chain or heavy braided steel wire attached to a specially designed spinning head. This head is connected to rods that are extended down into the chimney flue or up from the bottom. A heavy duty drill spins the rods and chain head at at a very rapid speed. This process then scratches the shinny glazed creosote off of the walls of the flue tile. More often then not, we are successfully able to removed about 90% of this shinny creosote and return the tiles back to their original orange color. be careful not to choke the stove down to much, burn very season wood and be sure the chimney cap screen is kept free of any creosote buildup.
The dryer vent cleaning is another service that we and many other professional chimney sweep companies offer. Their are specific procedures to follow such as no screws or plastic vent piping should be used in the venting system. The accumulative length of the dryer vent run should be calculated and evaluated with proper metering and recorded before and after the dryer vent cleaning. $150 does not seam out of line for a professional who knows what they are doing, insured properly and softer brushes and more flexible rods that are specifically designed for dryer vent cleaning. Here is little side bar, their are a lot more dryer vent fires then there are chimney fires and cause a whole lot more insurance fire related damage.
Burn Safe and warm and stay dry
I have a Queen Air Fireplace insert rated at 115,000 btu which was installed new in 1988. I am the second owner of the home, I have been using the fireplace to heat the home during the winter months here in Michigan. My flue is 12 x 12 clay I installed a cap on it 4yrs ago only because I was seeing water on the inside and rust had formed, but since then I have had a lot more creosote build up near the top of the chimney, I burn dry seasoned Ash wood only, have it cleaned twice during the six months of use and I burn on the average of 7-8 cords. My question is can the cap/screen be restricting or dampering down to much for this unit? is it possible that it was made to burn with a open flue? also seeing that I have some now creosote build up any thing I can spray or brush on to help break down over fall here before season starts back up? Thanks Dave
I recently installed (3 weeks ago) a flexible stainless steel liner insert for a wood stove that have start using for the first time this year. Recently whenever I turn the dumpers down and head to bed or leave the house (so the fire won’t go out), I have been having problems with Creosote coming out of between the joins in the stove pipe above the wood stove. When I first noticed it I killed the fire, took apart the stove pipe, cleaned it and the applied a joint adhesive/sealer for stove pipe. The Creosote has seemed to have made its way through the sealer and is now coming back through the joints, again. This is all within 2 days! What should be done? I some need advise/solutions to help fix this problem, please.
Thanks.
Take a moment and look at our videos of wood stove installation, firewood and also on creosote on our website http://www.askthechimneysweep.com
I would request the service company in writing, to return and explain the problem and how it will be resolved. In thirty year of business I personally have never had to use sealer on any pipe joints. I personally believe smoke will always take the path of least resistance and will rise up in almost all properly sized venting systems. Remember, I stated properly size venting system. This means not down sizing the chimney flue system.
Most building codes state that any solid flue burning appliance, the flue pipe size must be the same as the exit on the wood burning appliance.
The screen on the chimney cap needs to be kept clean or totally removed.
You cannot choke down a stove and not expect glazed creosote problem.
Your firewood needs to be seasoned. This a very serious issue and must be resolved. I hope this shed some light on your creosote problem.
Burn safe and warm
Clay
We are having an issue with creosote weeping through the masonary work of our chimney. We have an 8 inch block chimney with a liner. We are using a 6 inch flue out of the stove. How do we stop the weeping?
Do you have a solution to the creosote buildup on the ceramic glass door of my fireplace insert? Seasoned wood and high temperature are necessary but some deposit is still going to happen. Are there any recommended ways to clean off the window. I have used soft scrub for stove tops with pot scrubers with some success. Are there any other solvents that will work? Thank You.
I have a new wood burning stove insert complete with a new flue system. The stove has a catalytic combustor. Are these chimney sweeping chemical logs/sprays safe for the catalytic combustor?
Thanks in advance for the advise.
@TomLaw2 – Sorry, further search of your site answered my question. Bypass the combustor for an hour after application of the spray. Thank you.
Lea,
It sounds to me like you do a lot of burning. I would recommend calling in a professional chimney sweep. It sounds like you may have an issue with improper lining. I cannot be sure because I have not inspected your fireplace. So again, I would call in a Chimney Sweep.
Burn Safe and Warm,
Clay
I’m not sure, I would check your local hardware store.
I know this doesn’t seem like much help but, I would check the manufactures recommendations. Look through your manual or even look for a contact number or website. Do this before using any chemical cleaners.
Burn Safe and Warm