Creosote Removal

Creosote and tar build up in chimneys and flues

The burning of wood and other fuels in your stove will produce soot and other bi-products.  The use of good, seasoned wood that is burned efficiently will reduce the build up of deposits in the flue and regular cleaning as advised by your chimney sweep should be all that is required to keep your appliance and flue working efficiently.


Creosote is a bi-product of incomplete combustion and is an indication of improper use, unsuitable fuel, poor installation or poor stove design.  


Any deposit in the flue can be the cause of a chimney fire, but a build up of creosote is the most difficult to deal with. If you are aware that you have creosote in your chimney please do not ignore the problem.  Chimney fires can spread and destroy your home.  The intense heat of a chimney fire is likely to damage your chimney, stack or liner.

Three stages of creosote

There are basically three stages of deposits that build up in a chimney.


Stage 1,or first degree is a dry, sooty deposit that usually indicates the burning of good quality, well seasoned wood.  It can be easily removed by regular sweeping.


Stage 2 or second degree is often referred to as "clinker".  These deposits are harder flakes and lumps that stick together.  They are usually still soft enough to be removed by our normal sweeping methods.  The presence of stage 2 creosote indicates a problem either with your fuel of the way your stove is being used.  Your chimney sweep should advise you further if this is found.


Stage 3 or third degree.  Also referred to as glazed creosote or tar.   This is a thick black or yellowish deposit that is foul smelling and runs down the flue, into brickwork and oozes out of any openings.  When the chimney cools, it hardens into a layer that sticks to the side of the flue.  


Stage 3 creosote is usually impossible to remove by normal methods of sweeping.  It is highly flammable and continued use of a chimney or flue with this problem is dangerous.  Your chimney sweep will probably advise you not to use the fire or appliance until the problem is put right.

Common causes

The most common causes of creosote build up are:

  • The use of wet, unseasoned, treated or unsuitable wood or fuel.  Unseasoned softwood will create a problem very quickly.
  • Running your fire or stove at too low a temperature.  Slumbering the appliance for long periods of time mean that the fuel is incompletely burned which causes creosote to build up.
  • An oversized chimney or flue that allows deposits to condense in the flue.

How we treat the problem

Creosote treatment with Cre-Away Pro

Cre-Away is a four component powder that safely and effectively modifies glazed or third degree creosote so that it can be more easily removed by chimney sweeping.

First,  a reactive agent neutralizes the slightly acidic creosote making it less corrosive to metal components and less flammable.

Second, a dehydrator absorbs the oils and moisture contained in some forms of creosote.

Third, a combustion inhibitor helps to reduce the chance of chimney fires.

Finally, a magnesium catalyst helps break down third degree creosote when the flue is heated by normal use.

How we do it

  • We first sweep the flue as usual to remove all loose soot and deposits.
  • The flue or chimney is then pre-heated for around 30 or 40 minutes using a propane heater.  This prepares the chimney for the chemical treatment and aids convection in the flue that will help carry the chemical powder all the way through the flue.
  • Using a compressor and special applicator, the Cre-Away powder is then sprayed into the flue to fully coat the creosote.
  • Over the  next few days the client uses the fire or stove as normal. It is important to heat the flue it is during the heating and cooling cycles that the creosote loses its adhesive properties so treated that it can be more easily removed.
  • Cre-Away modifies third degree creosote by converting it into a more brittle state that has a different expansion/contraction rate than the flue it is attached to.   After a few days we return and sweep out the modified creosote using the appropriate method for the flue.

How long does it take?

The time it takes to chemically modify third degree creosote will depend largely on how bad the existing build up is.  In many cases we can remove the creosote with just two visits over a period of a week or so.  More difficult build up problems may require multiple treatments to fully resolve the problems.  We can advise you further on inspection.  


Please remember that creosote is a dangerous hazard and should not be ignored.  The longer the problem is ignored, the harder, and more expensive it is likely to be to resolve.   If you can see or have been advised that you have a creosote problem please call us.