How To Remove Creosote and What is Creosote?

Stage one creosote is very powdery, like the pile above.

What is Creosote?

Creosote is a flammable and corrosive substance that can build up on the walls of your fireplace and chimney. Creosote forms when unburned wood particles, fly ash and other volatile gasses combine as they exit the chimney. If there’s a poor draft, these unburned particles and gasses can condense and build up on the walls of your chimney. Over time, these e 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, releases by the initial fire, or primary combustion. Burning wood, no matter when releases pollutants in the form of gasses and particulate matter. Flue gas, comprised of steam and vaporized but unburned carbon based byproducts (vaporized accumulation). If smoke exiting the chimney is cools to below 250 degrees Fahrenheit, the gasses liquefy, combine, and solidify to form that tar compound. 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:

This swollen creosote is very fragile and brittle. It can block the flue and cause tremendous smoking problems. Not uncommon if you’ve experienced a chimney fire.


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 “tar build-up.

Fragile 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.

Often creosote will accumulate at the top of the chimney over longer periods of being unattended to during the events.

Creosote Glazing

Glaze forms in the solidification stage and occurs when new layers of creosote build 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 break down by chemical treatment. The two best products to use To remove this hard as a rock glaze, it must firare Anti-Creo-Soot 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. This converts 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. When this happens, the ACS Powder causes the creosote to expand and contract at a different rate than the flue it’s attaches to, causing it to pee
l away from the flue liner. Both of these products contain unique chemical catalysts that break 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.

In conclusion, 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.

After this, remember to check out our Youtube channel and other blogs!

Read here if you having additional odor issues with your chimney.

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Clay Lamb
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90 thoughts on “How To Remove Creosote and What is Creosote?

  1. My guess would be the creosote was trapped in behind the new chimney liner and is heating up and dripping back down? (or) that the chimney cap spark arrestor on top of the new liner is getting clogged up because it is being dampered down way to much and not getting hot enough to push those gases, up and out of the flue liners
    … Keep an eye on he spark arrestor

  2. According to where your saying these brick are located, they should not be within the interior of flue and the will restrict the up draft. The mason “may have” have used them to temporally support the other brick during construction, or to get around some kind of framing or piping obstacle. To see what is under or behind these bricks I would have them removed and then covered over smooth, with masonry and just as important to remove that draft restriction.

  3. Sorry but even after 44 years of marriage,
    I’m not qualified as a marriage counselor,
    ….. but I sure do like the way your thinking!

  4. My thinking is that they are what as referred to as being in-cased.
    Many time we had to cut into the side of the brick chimney to get them moving,and other times we had to tear down and start over.
    Flue tiles today are suppose to have 1/2″ to 4″: of “airspace a round them during construction.

  5. It will not be easy as it has now been heated up and liquefied back down into the pores of the cement block.
    Sorry to say, I’m thinking removal is the only safe way to approach this!

  6. Hey there – I have a question for you – we recently purchased a small vermont castings wood stove. Installed it where our old wood stove was, which had an eight inch pipe (this one is 6) – used a converter at the wall to make it fit our hole, and within 3 days of use had creosote dripping from the screw holes in the pipe. Needless to say, we need a liner for our chimney to increase draft. My question for you is how to get this insane amount of creosote out without damaging the inside of our stove. It’s all crusted up and down in the back of the stove, and covering the inside of the pipes. Should I use one of the cleaning logs? should I take the whole stove outdoors and just burn it really hot for hours? Help! (and Thank you!!)

  7. For the benefit of our other readers lets start with this; I would not hesitate calling the Vermont Manufacture customer service department and seeking their advice (first). Vermont makes a good line of stoves, and I have use one for many years prior. I feel that this is a fixable situation. Clogged chimney cap screens are all to often part of the problem, as well as burning wet wood and choking the stoves damper down to much. At this point not being able to see this installation, taking the stove outside sound intersting, as it would allow for a more of a controlled removal of the creosote either scraping, chipping or heating up isolated individual interior stove parts. I would not extinguish any smoldering or flame with water, as it more than likely could crack the the “cast iron foundry produced parts”.
    I would agree that the 8″ pipe is to large, or what is referred to as being “over sized”. Stove pipe and chimney liners that are attached to a stove need and must be by most manufactures be the “same size as the outlet on the back of the stove, in your case (6”) as you stated. I will say that many of our customers use those Chimney Sweeping logs. I will say they appear to dry the creosote, making it a much more sweepable consistency, but we have not seen these logs “remove the creosote”. If you have black pipe that is gummed up it may be easier just to replace it!

    Strictly for story line purposes here, years ago a number of sweeps tried a method referred to as flaking. This was supposed to be a controlled burning of glazed creosote chimney flue by slowly lowering a small flaming basket down the chimney in hopes of the fire only burning upwards, and not getting out of control and burning downwards. It is not to difficult to imaging what happened as things got out of control and to often cause more fire damage to the flue.
    I hope this helps, but again start with the manufactures directives on resolving your issue!
    Special Regards,

  8. I have an indoor wood burning furnace that has a barometric damper on it per manufactures instructions. Every so often I have to clean the damper flap from the creosote build up. I now have the glazed creasote on it and was wondering if I take the flapper thing off and spray it with the ACS, would that remove it. Or is there another product I should use on it?

  9. Martha,
    I would think the wood is to wet, the chimney flue is not size properly or that the equipment is being choked down to much and maybe causing this creosote build up problem. Sorry I can-not speak for the Mfg. of ACS or the Mfg. of your furnace equipment.
    I will defer your question at this point and your contacting to both Mfg’s since this could be a serious situation, and should be addressed.

  10. Hi. We don’t have any chimney sweeps in my area. I paid one to come from an hour away, but he didn’t help my problem. I have a chimney with a fireplace in the basement and one on the first floor. I don’t want to use it, but the smell from the creosote is bothering me as it smells up the entire room on the first floor and then some. He said the basement fireplace had a leak in the flue or didn’t come out the chimney correctly and it built up a lot of cresote. The only way to get to it is the ash dump on the first floor or a small hole in the basement (that fireplace was one of those black stoves). He put insulation in the ash dump on the first floor and told me to clean the inside of the fireplace and hearth with equal parts ammonia and water. That didn’t help. I had my dad open the ash dump and put spray foam on top of the insulation and then use silicone caulking to seal up a metal plate over the ash dump. Is that okay? Is there any danger to doing that if it works and I don’t plan to ever use either of the fireplaces? Or do you know anything that could help me? I appreciate your help more than you know!

  11. Your asking Is it OK, … just might be a little late!
    When ever I have I have a problem I find a way to fix it, as you did! Get IT Done!
    My caution is to your “possible” liability exposure, that is if the property would be sold in the future.
    Be-sure to document it——->”These are not functioning fireplace(s), and that they are only decretive.
    . . . Isn’t it nice to have Pops around to help you! :-))
    Clay Lamb

  12. I know! Lol. I just figured I could take it off if it wasn’t a good idea. I didn’t know what else to do. I’ve searched and searched on here and I haven’t found anyone with the exact problem I’m having. I didn’t find your site until after I had done it. I just wanted to make sure it wasn’t a fire hazard or anything if it was unused. Thx so much!! @Clay Lamb

  13. I have a wood fired boiler that sends hot water into my house.When I am done heating for the year I am left with a hard tar like substance all over the inside of my furnace and the metal chimney. thanks

  14. Without seeing your equipment and venting system here is my laundry list of potential culprits to your glaze creosote problem.
    I might guess that you have a clogged up screen on the chimney cap, often this is caused by choking the damper down to far or to often! To many elbows in the connector pipe from the boiler to the chimney. Burning wet wood that has not been seasoned, covered and dry for 6 month. The size of the chimney should not be reduced, an should be the same size in inches, as the opening on the back of the boiler ( ie; 6″or 8″ in most cases). …that is “unless the manufacture states in writing that it can be changed in size.
    Cleaning only at the end of season may be also be a reason for this creosote accumulation!
    Since your concerned about this situation (and rightly so) it may also it may be time for a video evaluation of the entire system!
    You should be able find a reputable Chimney Sweep in your area by using this link to the National Chimney Sweep Guild locator :
    Also be sure and go online and read their customer reviews from Google, BBB and AngiesList.

    Be Safe,not sorry!
    Clay Lamb
    Here are 4 videos from my Ask The Chimney Sweep video library that may be of help!

    Chimney Creosote Removal & Odors

    Levels of inspections

    Chimney Fires

    Types of Chimney Fires

  15. Brenda, I will assume you referencing the ceramic tile on the front of your fireplace.
    The only product that I have had success with is called “Paint”N”Peel” and it is made by SaverSystems
    It works just like it’s name implies. Paint it on, we wait one day and peel it off!
    Check out our Ask The Chimney Sweep video –>
    You may find it locally? If not, I liked the product so much I added it into my e-store

  16. Every fall I get a bucket of light flakey creosote that the summer weather has knocked loose in the flue liner. Pull out the woodstove pipe and dig it out of the bottom of the chimney.
    What happens if I add some of this back to my fire? Seems like free btus.

  17. I have a Lopi Republic 1750 wood stove insert. The chimney is inside of the wall. When I run by brush down from the roof all of the creosote ends up in a box of some sort of top of the stove. The problem is, I cannot reach the box to empty it. I’ve tried to reach with a normal shop vac but can’t get there. What do you recommend I do?

    Thank you

  18. I have not heard of this re-burning the creosote before. Sounds just a little scary for me to try. So digging out the pipe tells me your burning wet or unseasoned, just a whole lot of wood or choking the fireplace down to much. A big caution on all three burning practices, make you a serious candidate for a unwanted chimney fire.
    I have attached four of my videos that may be worth your watching!
    Burn Safe and warm!


    * SIGNS OF a chimney fire * Sudden Occurrence Insurance Claims

    * ChimneyFires:

    * Sudden Occurrence Insurance Claims

    Clay Lamb author of: – Youtube Educational Videos – Professional grade Chimney products – Contractor Coaching Podcast – GM @ American Chimney Sweep Cincinnati, OH

  19. I will assume the “surround” that your mentioning is the brick “Chimney case” as seen from the outside of your home.
    I will also assume that both of your fireplaces and flue systems are housed in this case as well as possibly a gas furnace or even a gas hot water heater flue system.
    The term in our industry that is associated with this problem is referenced as Thermo Siphoning or a Negative House Pressure.
    I believe you’re on the right track about heating the lower fireplace, but as you mentioned ut it is not a practical long term solution.
    Here are a few ‘Possible solutions;
    1st) Verify with a camera that there are no gaps in either or both of the chimney flue systems.
    This can be completed with a level 2-chimney inspection with a camera by professional chimney contractors then you can decide if the repair is warranted
    2nd) I have seen in the past where raising the upstairs chimney flue line 6”-12”, resolved the Thermo Siphoning problem.
    I have included a link to the Nation Chimney Sweeps Guild that may help you find a Chimney Contractors in your area. Also remember to check references on any your home Contractors on Google, Yelp or AngiesList before signing a contract for repairs

    If you have time, watch this video with my buddy Jerry Isenhour, who does a great job explaining the causes of this problem.

    National Chimney Sweep Guild locator:
    Clay Lamb author of: – Youtube Educational Videos – Professional grade Chimney products – Contractor Coaching Podcast – GM @ American Chimney Sweep Cincinnati, OH

  20. Hello Mr. Lamb, I have recently encountered a problem with my my wood furnace which has been converted to burn sawdust. If you are not familiar with sawdust burners, they operate on a principle similar to pellet stoves. The problem I have is the chambers inside the furnace all have a coating of glazed creosote on the surfaces. I have been using the sawdust burner for four years and have never had this problem before. The weather pattern in my area has been cool to cold at night but comfortably warm during the day. This causes the furnace to run regularly during the night but to idle a lot during the day and as a result not create sufficient heat to draft properly. Can you recommend a procedure to remove this glazed creosote? I have had at least one fire in the furnace chambers above the fire box and I would prefer to prevent any further occurrences. I strive to maintain the heating system and try to clean it once a month during heating season. This may seem excessive but I would rather put the work in than have a chimney fire. The main reason for the frequent cleaning is because the pipe connecting the furnace to the chimney although only 4 to 5 feet in length, is at a very low angle. It has a rise of only 6″ over its length. Any suggestions you can give will be greatly appreciated. Thank you for your time in this matter……..Steve Manzer

  21. Steve, thank you for addressing meas Mr Lamb, but I’m just good “old” Clay .
    Let me try and unpack this as to how I personally would try and resolve this creosotes problem.
    First off I “have not” worked on a furnace that has been converted to burn saw dust.
    Although this sounds rather straight forward, I would stop everything and contact the manufacturer of this equipment.
    I would want to speak with someone in their engineering department and ask if they have had any experience in this type of conversion to use sawdust as the primary fuel source.
    You mentioned that your furnace operates on a principle similar of a pellet stove.
    I will assume you have an auger and hopper to feed this fuel into the furnace combustion chamber?
    And that this is now being coated with glazed creosote on the surfaces.
    Since you have been using this sawdust burner for four years and have never had this problem,
    I would think that something has changed in the venting system!

    Steve this is a list of what I would go looking for first!
    As you mentioned the weather pattern in your area has been cool to cold at night, but comfortably warm during the day.
    Also that this causes the furnace to run regularly during the night, but to idle a lot during the day and as a result not create sufficient heat for the chimney to draft properly.
    I would check the bird/spark arrestor screening on the cap on the chimney top at different times of the day, night and especially in the early mornings.
    I would want to see if creosote is accumulating or freezing up on top and possibly blocking the draft.
    This is especially true after it had been choked down at night or after your going off to work?
    Your mentioning of having at least one fire in the furnace chambers above the fire box, causes alarm to me.
    This is a very serious fact, that should be addressed with a video camera scanning of the interior of the “entire” chimney flue system. Most chimney sweep contractors should be able to preform this type of service for you. If there is chimney flue damaged, this video image verification could be supplied to your insuracne carrier so that you could begin to make a “Sudden Occurance” insurance claim. (See my list of attached video)
    It makes no difference, if you have a clay flue tile chimney flue or a class A mental chimney system,
    the interior of the chimney flue pipe may have been damaged in a so-called “quite of slow” burning chimney-fire.
    This type of interior flue damage may now be causing a serious blockage or additional dampening of the chimney fuel gases, and may be preventing the proper venting of the smoke.

    Also be aware that cracks or missing mortar joints in a clay flue tile system may have developed after a chimney-fire, and may now be acting as a “straw with holes in it” and may now be stifling or restricting the chimney draft flow.
    As a separate issue their are many different types of creosote modifiers on the market, some are liquid and some are granular. Use these products as directed on their packaging. All of these modifiers seam to work to some extent, in changing the consistency from that (stage 3 degree) “tary” creasote, back to a dusty or sweepable (stage1) creasote consistency.
    Your striving to maintain the heating system and cleaning the system once a month during heating season, does not sound to agressive to me at all.

    When you stated “the main reason for the frequent cleaning is because the pipe connecting the furnace to the chimney is only 4 to 5 feet in length, and at a very low angle, may need a little more clarification for me.
    If I’m hearing this correctly, in most cases this would not be the culprut, as most building codes that I’m aware of require a rise of ¼” per foot of any horizontal run. I think that this is being coverd in your 4’-5′ horizontal rise statement?

    Without physically seeing your installation, that the breach opening on the wall where the chimney begins it venting up the chimney “must be higher” than the exit outlet on the furnace equipment and must maintain that 1/4″ per foot of horizontal rise on that connector pipe! This is required so that it provides for a good draft flow of the smoke from the furnace, again up the chimney with out any stalling.

    Steve, I hope that this bouncing of ideas, helps you in identifiy and solving this creasote problem that your experiencing

    Burn Safe & Warm
    * Sudden Occurrence Insurance Claims

    * SIGNS OF a chimney fire

    * Creosote Removal:

    * To find a reputable Chimney Sweep in your area, use this link to the National Chimney Sweep Guild locator:
    Also be sure to go online and read all of their customer reviews from Google, BBB and AngiesList.
    Clay Lamb author of: – Youtube Educational Videos – Professional grade Chimney products – Contractor Coaching Podcast – GM @ American Chimney Sweep Cincinnati, OH

  22. Placed a piece of wet Larch on the shelf above wood fire door. Unfortunately, it seeped pitch onto the metal. Is there any way to remove pitch? Will Goo-Gone work? Just paid $3500 so don’t want to ruin surface.
    Thank you.

    Annie in Montana

  23. Annie, I’m sorry to hear this. I have no ideas what would happen if you used this product.
    I really don’t have any idea where to go with this problem.
    I guess I would just keep on Googling and then try sample areas.

  24. Sir
    The inside of the bonnet, on the top of the stove pipe, above the roof, has a hard bubbled up surface of creosolte. Gas won’t cut it. Will your product help dissolve it?


  25. I would say after reading your question, there might be another issue for this hard bubble accumulation.
    I would recommend contacting a Chimney Sweep in your area to validate the degree of creosote accumulation,
    and possibly if you “may have” experienced a chimney fire damage, that “may or may not” be covered under
    your current Home Honers Insurance policy.
    Clay Lamb
    * Here are a few Youtube videos that we have produced here at Ask The Chimney Sweep that may be of some help!
    * Also, I have included a link to a Chimney Sweep finder, that you just pop your zip code in, and a few members of the National Chmney Sweep Guild will show up for your given area.

    * Creosote Removal:

    * SIGNS OF a chimney fire

    * Sudden Occurrence Insurance Claims

    * Creosote Problems
    PCR Video for homeowners

    *Chimney Sweep Locator, by Zip code
    To find a reputable Chimney Sweep in your area, use this link to the National Chimney Sweep Guild:
    Also be sure to go online and read all of their customer reviews from Google, BBB and AngiesList.

  26. I have brick chimney that has no liner ,it was usedf for hot air oil furnace.It is about 30 feet high. I hooked up a hot water combo kitchen stove boiler it heats domestic and baseboard heat. Plus you can cook on top and oven to bake. Love it ! Came from Austria. They do not mke them anymore. Everyone I talked loves them.Well you can burn wpod ,coal,coke anything.but flammable liquids. I have it for 3-4 yrs.had chimney checked guy said great shape for 100 yrs. old.Well stove has to have very dry wood .2 yrs. Old I am getting a lot of glaze tryed everthing getting bad .Jad guy come out he said use cre a eay been gets about 1st 10 feet and then back to HEAVY GLaze WHAT TO DO????? Pastor Jeff I restpre stoves and instal. Never seen this bad before HELP!

  27. Your job seems extremely complicated and I would highly recommend getting 2-3 chimney contractor resources from your own backyard to bid on this.To find a few chimney contractors in your area, here is the link to the National Chimney Sweeps Guild. Always beside to check Google, BBB and Angieslist for reviews be for signing any contract.

  28. In addition to getting a few more opinions I want to state that creosote issues are most often from a couple of sources, such as wet wood, slugging draft of not opening the stove up early enough in the morning to allow those gases to vent out of there, or a blocked chimney screen up at the top of the cap. Here are a few of our videos covering creosote issues:

    I hope this gives you a little more insight of the creosote problem.

    Regards, Clay

  29. Hi!
    We have always had a bit of an issue with creosote dripping from the under side of the chimney cap, and if there’s any wind it blows it onto the side of the house. Until last year we had wood siding and it would wash of real easy with my little pressure washer. But last year we had vinyl siding put on, and it did the same thing, but the creosote won’t come of at all with any soap or pressure or scrubbing that I have tried. I searched for a product that will clean it, but while some products say they will, I read reviews and forums, and people say that it doesn’t work. I’ve seen where people have said that they take their chimney cap off during the winter months so it can’t build up and drip from the cap, but I’m skeptical about that as well. The wood that we burn is always under 10% moisture content as well, so we’re not burning green wood. Any advice or products you could recommend?

    Thanks in advance!

  30. Lets start in reverse. 10% moisture content is really good for wood so I question what may be causing the creosote in the first. Most commonly its the cause of choking down the damper too tightly, not allowing it to vent properly. If its an insert, you may want to flush it through the doors with a fire every morning with a fire for about 20 minutes. You may also want it get it relined with a properly sized pipe that extends from the top of the insert to the top of the chimney. I’ve attached some videos about relining for you. As far as getting creosote off of vinyl siding, I have no recommendations. That will probably be trial and error. Hope this helps!

    Clay Lamb.

  31. Thank you for your response Clay!

    We’re not using an insert, we have a wood stove that’s only about 4 years old. You mentioned choking down the damper too tightly. So, the way we use it normally is to get a good fire going and build a good bed of coals, and then for days we can fill the box and keep the fire going all day while we’re at work and all night while we sleep without having to re-light it. Our damper doesn’t actually completely close, (I don’t know why, it was made that way), but we close it as far as it goes, or very close to it, because if we don’t it tends to make the house too hot, and/or the fire doesn’t last as long as we need it to and we have to restart the fire instead of being able to just add wood to the hot coals. So I guess I would ask, is there something wrong with our process? Should we need to re-light the fire at least once a day or something?

    Thanks again!

  32. I think its a long period of time that its just smoldering in the house. Because the chimney is cooling down and solidifying creosote on the walls, I think its going to be trial and error as its a long period of time creates creosote accumulation. Leaving the damper too tight is the only thing that comes to mind, I’d have to do a fuller investigation to know what to look. I would recommend using the sweeps finder on this site: Sorry, I haven’t been able to shed some more light on this. Dont hesitate to reach back, Clay.

  33. My mobile home had railroad ties in the crawl space for many years. Although they have been removed, there is still a lot of creosote vapor that gets into the house. What’s your recommendation to get rid of the creosote vapor?

  34. I have no idea, I apologize. Creosote is always flammable, just always be conscious. That’s cariogenic and cancer-causing, so be very, very, very cautious. Wish I had more insight for you. Respectfully, Clay.

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