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Creosote: Causes and Why it is a Concerning Hazard
What is Creosote?
Creosote is a natural byproduct of burning coal and wood, made from a combination of soot and tar. It is highly flammable and presents itself to be a black, sooty and tar like substance. Every wood and coal burning fires produces smoke that contains hot gases, soot, particles, and creosote which covers the chimney’s interior flue system. The presence of creosote should not be taken lightly, it is neither rare nor harmless. It is an inevitable hazard that anyone with a wood/oil burning appliance will face. Creosote appears in three stages, depending on the amount and type of buildup found on the walls of the flue. This byproduct is known to be sticky and difficult to remove as it requires a more extensive treatment than a normal chimney sweep service. It is very concerning to have creosote in your chimney; not only is it a flammable substance, but it can also create a serious obstruction in the venting system.
Soot is made up of carbon, but creosote is made up mostly of tar–a sticky substance that is also flammable. Because of the sticky nature of creosote, it collects easily in a chimney, covering parts, thus clogging the clean out area, and creating a fire hazard. As creosote builds up, it can become a serious obstruction–and when it reaches stage 3 buildup it is also difficult to remove.
Stage 1 Creosote
In the first stage, it presents to be flaky black soot. This occurs when the air in the flue is cold and then quickly warmed by the fire’s heat. This is one reason it is essential to properly warm your flue before starting a fire. One way to warm the flue includes, holding lit cardboard or pieces of paper inside the firebox, directly under the flue. A basic chimney sweep service should more than likely be able to remove this form of creosote.
Stage 2 Creosote
Stage 2 creosote appears as shiny, hard black flakes. This stage forms when there is a restricted amount of air flow, trapping the smoke inside the flue of the chimney. It is more difficult to remove this stage of creosote because of the hardened tar like substance, but it is likely that a rotary loop can clean it out.
Stage 3 Creosote
The last stage is also known as glazed creosote. This is formed when the chimney is not regularly swept. When creosote is left untreated and the homeowner continues to burn wood, the high temperature in the flue will cause the creosote to boil; the moisture will evaporate and leave a thick layer of hardened concentrated fuel. Glazed creosote is the most dangerous form because it can easily be ignited and cause a chimney fire. It is also the most difficult to remove. Stage 3 creosote cannot be removed without damaging the chimney liner; it cannot be swept out and it is likely that the homeowner/handy man will cause damage if they attempt to do it themselves. It is crucial that the homeowner understands how much of a hazard this has the potential to be, and what could happen if it is left untreated.
Can Creosote be Prevented?
Unfortunately, no. Any wood or coal burning appliance will produce creosote, even if the homeowner is taking additional steps to reduce creosote buildup, such as burning creosote logs, etc. One cannot prevent creosote from forming, but it is possible to prevent the buildup of it if the chimney is swept regularly. Burning wet or “green” wood that is freshly cut will not burn efficiently and will cause more creosote. It is recommended to only burn properly seasoned firewood to ensure the fireplace and chimney draft effectively. However, even doing this will not prevent the formation of creosote and we strongly recommend the system be swept and inspected on an annual basis. If you have a moisture meter, it is recommended that properly seasoned wood have a moisture content of below 20%.
How do I Know if my Chimney has Creosote?
Having your chimney inspected by a certified chimney company will guarantee whether creosote is present in your chimney. It is crucial that a level 2 inspection is performed; this would be done with the use of a 2 headed camera, which is sent up the flue of the chimney. The technician will be able to distinguish the level of creosote (if present) based on the camera scan as well as other potential hazards such as, cracking/deterioration in the flue tiles, missing mortar joints, and more. Creosote buildup gives off a strong bonfire smell even when the fireplace is not being used, especially when it is wet/damp outside. If you experience this, do not use your fireplace, and call a certified chimney professional. Not only can it destroy the flue and cause a chimney fire, but it is also harmful to breathe, and it may irritate your skin.
Is a Sweep Service Enough?
It is important to note that having your chimney swept regularly does not ensure the system is suitable for use and meets the codes and standards written by the Chimney Institute of America or the National Fire Protection Association. A level 2 inspection must be performed before any certified technician can accurately state whether the system is suitable for use, or offer a proposal for any form of replacements, additions, or repairs.