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Originally published in the October 2017 issue of Sweeping Magazine

Question: What's the most effective way to sweep and remove creosote from a clay tile lined fireplace flue in a masonry chimney?


by Mike Segerstrom 


There's no one answer that will meet the variety of soot and creosote conditions we encounter. With advances in the tools and techniques of our industry, we now have several effective approaches to consider. The CSIA indicates that soot and creosote should be removed from a chimney flue when deposits of 1/8" thick or more are present. It is the type and extent of soot and creosote buildup, that plays a big role in determining what the best removal method is. Chimney and roof access may also be contributing factors.


For many years, brushing from the top with round or flat wire brushes was the standard. These brushes and this method can be effective when there is a powdery build up, and even when a thin layer of creosote glaze is present.


Rotary sweeping methods from the bottom with nylon or poly rods attached to a drill, using a variety of poly brushes and steel cable whips have now become quite popular. And these are also effective for removing powdery creosote and thinner amounts of creosote glaze.


When creosote glaze becomes thick and not flaky, it can be very difficult to remove with traditional methods from the top or bottom. One method that was very popular for many years, and still is in areas, is the use of chains attached to metal or poly rods, and rotated mechanically in the flue. Over the years however, some sweeps have found that this method may result in damage if a chimney flue liner is not in good condition.


There are also different chemical removal methods. Some products specify application while the fireplace is in use. This may be considered to help reduce or prevent creosote buildup, but caution should be used making this recommendation when significant combustible creosote and creosote glaze deposits are present in the flue. Operating the fireplace when hazardous glaze deposits are present, may result in a chimney flue fire.


Other products may be applied to the flue when not in use, and then the flue thoroughly swept after the product has remained in place for the required amount of time. Recent years have seen the introduction and popularity of a unique product known as a poultice creosote remover. This product is generously applied to the creosote glaze in flues and smoke chambers, and when applied correctly and allowed to remain in place the appropriate amount of time, it is extremely effective and makes sweeping/servicing the flue and removing creosote very easy.


The advancement of chimney inspection techniques and processes has also impacted the sweeping of chimneys. Many sweeps now thoroughly inspect a flue prior to servicing it, when significant soot and creosote deposits are present. These inspections will include performing and internal camera inspection. Though the flue is dirty, it can provide useful information about the flow of flue gases through the chimney, factors for determining potential causes, and even provide a different view of defects or damage.


Whether or not the flue has been inspected prior to sweeping, it and the fireplace system should definitely be thoroughly inspected afterwards. We should pay close attention to areas of the system where creosote may have migrated to locations we cannot service, including but not limited to outside of clay liners through cracks and voids, and into the chimney structure through corbels and gaps in the masonry.


Equally as important as sweeping and inspecting the system, the client should be thoroughly interviewed to gather information that may help determine the cause of excessive buildup, or creosote glaze formation. Through the entire process we may be able to offer recommendations to help the client reduce this buildup in the future, which may help prevent a chimney flue fire or even potentially a tragic structure fire. In addition to recommending maintenance or potential hazard repairs, good recommendations for better operation and performance of the system often come from having a better understanding their fuel quality and burn habits.


Regardless of the sweeping or creosote removal tools, equipment or process, we should also always remember to protect ourselves from exposure, and the client's home from soot and dust.

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