Monitoring Creosote Buildup
If you have a fireplace or wood burning appliance, you have most likely been told that you need to have your chimney annually cleaned by a certified chimney sweep to remove creosote buildup. Few people stop to explain what creosote is and why it is so important to get rid of. We don’t want to keep you in the dark. We have compiled the most important information that you need to know about creosote.
What is Creosote?
Creosote is the leading cause of chimney fires. It is a smelly corrosive material that is incredibly combustible. It is produced by combustion gases that are given off from burning wood. When the temperature in your flue is below 250 degrees Fahrenheit, these gases condense in your chimney and buildup along the lining of the flue. Since flue temperatures often dip below 250 degrees, creosote regularly builds up.
Extreme heat and burning embers that drift up through the chimney can ignite creosote buildup. If there is an extensive amount of creosote, the fire could spread to your home. It is because of the large number of chimney fires sparked by creosote that the National Fire Protection Association (NFPA), a nonprofit organization that has been committed to preventing fires since 1896, recommends annual chimney cleanings.
Stages of Creosote Buildup
Creosote BuildupCreosote takes different forms, or has different stages, as it builds up. Each subsequent stage is more hazardous and more challenging to remove.
Stage 1: In the first stage, creosote is soft and flaky like soot. Stage 1 creosote is easy to remove with a basic chimney brush.
Stage 2: Once creosote reaches the second stage it condenses into a hard, shiny flaky substance that clings to flue lining like tar. Though it may look flaky, Stage 2 creosote cannot be brushed away easily. The most effective way to remove stage 2 creosote is with a powerful drill that has metal rods called a rotary loop.
Stage 3: The goal of every chimney sweep is to stop creosote buildup from reaching this stage. Stage 3 creosote is a sticky, highly concentrated fuel. If you looked down a chimney with stage 3 creosote, it would look like tar was dripping down the inside. This tar-like substance hardens along the chimney lining and thickens as more creosote condenses. The thicker and harder it is the more combustible it becomes and the more challenging it is to remove. Chemical removers can be used in some cases to clean up stage 3 creosote. A rotary head with chains can also be effective when it has hardened and is not sticky, but this option is not recommended if you have a clay or ceramic chimney lining since the process can dislodge broken pieces of the lining. In many cases, the best option is to remove the flue lining and replace it.
Without proper equipment and training, it is smart to leave creosote removal to professionals.
Ways to Minimize Creosote Buildup
If you have a wood burning fireplace or stove, it is impossible to completely eliminate creosote buildup but there are ways that you can minimize it and prevent it from reaching stage 2 or 3 before your next cleaning.
The best ways to reduce creosote accumulation
1. Only burn seasoned firewood that has dried for 6 to 12 months. New wood contains a large amount of moisture. Wood with a higher moisture content produces more smoke when it burns. This smoke turns to creosote. The drier wood is the less smoke is created, the less creosote is produced. Buying a moisture meter will help determine when certain wood is best for burning. Make sure to split a log in half before testing since the outside or bark of a log may be dry but the inside is still holding moisture. (Wet wood also decreases total heat output since an extreme amount of energy is wasted in your fireplace on boiling and evaporating the water inside each log.)
2. Insure your fire has sufficient air flow. Air is an important ingredient for an efficient fire. If your fireplace has glass doors, it is wise to open them so that your fire can breathe. This will allow your fire to burn hotter which burns a greater amount of the combustion gases. Most modern fireplaces, stoves, and inserts are considered “high efficiency” – so opening a window or using an electric air collar may help.
3. Build hot fires that burn efficiently instead of slow-burning, smoldering fires. How you arrange firewood affects the fire that is created, pack it tightly—with modest gaps in between for airflow—so that it will burn cleaner. Make sure not to close the fireplace doors (ceramic glass) or restrict air flow adjustments too soon before the fire gets hot enough. A good indication that your fire may not be hot enough is if it starts to smolder and look like it might die out. At that point, the glass will also get dirty fairly fast and you are sending excess gases up the chimney.
Keep in mind high-efficiency chimneys are smaller than traditional masonry flues or decorative fireplaces so creosote build-up is even more important. New high-efficiency fireplaces also have re-burning features such as secondary air tubes and catalytic combustors that require high-temperatures to operate functionally and cleanly. Keeping cool, smoldering, small fires with wet wood is the surest way to build creosote in high-efficiency fireplaces and clog bird/pest screens.
4. Avoid burning artificial logs. Artificial logs create a large amount of combustion gases that condense into creosote.
5. If you chimney is on the outside of your house, warm the flue before lighting a fire. Cool temperatures in the flue create more creosote. A good way to warm the flue is to make a torch out of rolled up newspaper and hold the lit torch under the open damper until you feel the air warm and feel the draft reserve.
6. Use Creosote Destroyer Powder. Sprinkle a few tablespoons of Creosote Destroyer powder on a medium fire, use this every third fire to help prevent creosote buildup.
Removing Creosote from Fireplace Glass
With the above prevention methods we should be in good shape moving forward, but what about that dark stained glass you’ve got right now? The simplest and most effective method is to use a spray on Liquid Creosote Destroyer. With this kind of cleaner simply spray right onto the creosote and wipe off with a brush or cloth – you will want to wear gloves as it can irritate the skin. Friendly Fires also stocks high temperature glass cleaner. This cleaner helps keep the glass clean (do not use common cleaning liquids on glass).
Do you have any other methods you use for keeping creosote under control? If so, please let us know in the comments!
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I have a friend who soaks his green firewood in Kerosene for a week or so before burning. Does that work to cut down on creosote?
Hi Philip – this is the first time we’ve heard of this – so unfortunately, we do not have a good answer for you. We would tend to say ‘no’ – as its our experience that pure dry wood with a hot fire is the best option, but we can’t know everything! Thanks for your comment.
I have been using pressed logs. These are dry wood chips pressed into a log. I’m thinking they are amalgamated with some adhesive or wax but I’m not sure. I’ve bought these at the local hardware store. Is this dangerous or should I not worry?
We don’t know for certain what is in the logs you are burning as they were not purchased from our stores. But please consider the following:
1. Only real wood should be burned in todays newer EPA wood stoves and wood fireplaces (so any type of wax or filler is not recommended – for reasons explained earlier)
2. Even if those logs are simply wood – today’s newer appliances were not tested with that composition (ie increased wood density) – so if you put too many logs in your wood appliance, you could technically over-fire your wood stove.
Hence, we only recommend properly dried seasoned wood.
Hope this helps. Thanks for your question.
While most people have a chimney pipe thermometer, I also have a firebox thermometer. I get my firebox temperature above 200C (~400F) before considering to shut the damper unless my chimney temperature is above 250C (~480F). My chimney thermometer is about 12″ above the woodstove. I also push my wood away from the refractory in the back of my higher efficiency stove so the volatile gasses have more time to burn in the fire box before going up the chimney. While dry wood is essential to develop such a high firebox temperature, smaller diameter wood pieces, less than 3″ thick, aid in producing a fast hot fire. My wood stove manufacturer said I can also burn pine but it should be thoroughly dry, and I want my firebox with a couple of inches of hot coals and still over 300F before putting in pine wood. Hardwood kindling less than an inch thick, while it may produce very quick heat, it may also burn up a significant amount of its charcoal before the firebox reaches 400F or it may get the chimney >500F. Finally, when your wood is virtually all charcoal, you can just about choke off your firebox of air & oxygen without worry about creosote. As your woodstove temperature drops, you want to restrict how much hot air (which most likely comes from your living area) goes up the chimney.
Typically, how far away from the chemney can your appliance be, and does the pipe connecting the two require any sort of slope or can it be simply horizontal? Another question i have is does the height of your chemney above your roof affect draft or the appliance/chemneys ability to exhause gasses/smoke?
Wood venting and wood fireplaces all have their own clearance requirements, so we highly recommend checking your owners manuals. Generally speaking, wood venting requires 2″ to combustibles, whereas wood stoves and fireplaces require 12″+ (depending on the location, appliance, etc…) – but please check your manual.
Black smoke pipe can be installed in a horizontal fashion (with a slight rise), whereas wood chimney can be installed with a 15,30 or 45 degree angle if required. And yes the height of the chimney above a roof can affect the draw – both positively or negatively depending on the height.
Thanks for your question (and please refer to your installation manuals and local wood specialist for appliance and chimney specific information).
We have a pellet stove it lights really well. But does down fast. Sometimes it goes on an off many times. The glass turns black. We mess with the flew slot to see if that is the problem. But it just keeps going on an off. Be buy high grade pellets also..
Hi Pamela, Sounds like it may be best to contact your local fireplace store for a service call, as this could be related to a number of items and is tough to diagnose online. Best of luck.
I have my chimney cleaned annually. I start my fire with newspapers & kindling, with a regular sized piece of wood on top of all, in my wood stove. I usually let it burn hot for about 20 minutes before closing down the damper and door. The stove is in a room with just one story. Is this a sufficient length of time to heat up the chimney to burn off creosote? It feels hot to the touch and I always use dry wood. Should I also use one of those powder creosote removers? Is it safe to go to bed at night with the fire still fire going?
The best way to know if your chimney is clean is to inspect it visually from the inside (bottom and top), as well as run a brush down it on a regular basis. You can do this yourself or hire a local professional to assist. Once you do this on a regular basis, you will learn how dirty it gets depending on how much use. The best way to avoid creosote is dry wood (stacked, split, top covered in your yard for 2 years). If you are using dry wood, inspecting your chimney regularly, its been installed to code and burning it properly (per manufacturer instructions) – then yes – they are safe to burn all night.
Thanks for your question.
I clean the glass with a damp cloth dipped in wood ash. It’s efficient and costs nothing. 😀
I clean my glass with a razor blade. It comes off very easy.
I’ve always heard that using any shiny paper or shiny newspaper fliers adds to the buildup of creosote. Is this true?
Hi Carol, thanks for your question. It can but it’s not really enough to be a huge issue. I hope that helps!
hi there. i regularly clean out my chimney but am left with an ice cream bucket full of granulated dark creosote and ash. i am wondering what to do with it? i assume it is very toxic and has no practical application certainly can’t just be deposited in the garden or forest. any suggestions as to what i should do with it?
thanks so much, i am learning a lot here
Thank you very much for your comment. As for the chimney soot and creosote, it can be disposed of as you normally would any solid waste. Just put it out for the trash.
I hope that helps. Please let us know if you have any other questions at all.
the stove pipe inside my cabin is 18′ high. I try to keep the flue temp around 400 (thermometer is approx 24″ above the top of the wood stove). The flue pipe temp is much less at 12-15 ft. Will creasote develop where the flue pipe is cooler?
Thank you for the comment Jeff. What you describe is normal, and yes creosote will tend to develop where the flue pipe is cooler. Make sure you chimney is swept at least annually to keep everything in good shape.
What is involved with removing the pipe and replacing?
Its best to get a professional to assist, but some pointers:
1 – Locate the manual for your pipe, follow its instructions. Wait for pipe to cool
2 – Most black pipe is held together with 3 screws – remove them
3 – Pipe should have been installed with a slip or adjustable part – use it to slide the pipe up and down
It its insulated chimney you are looking to replace, we would recommend you hire a local professional.
Thank you for your question.
thanks for sharing. we work on representing modern Bistoon fireplaces and we see that modern fireplace are getting popular day by day.
My uncle throws in a piece of hemlock wood occasionally and that’s all he uses!
Thanks very much for the comment Robert, interesting idea!