Outline of Chimneys




Wherever a fuel is burnt, soot will form.  If wood is burnt, this soot often contains tar or resins that can adhere to the side of your flue.  Over time, if not regularly swept, your flue can become coated in thick layers of tar, or creosote.  It is highly flammable and not possible to remove with brushes, especially in older chimneys where soft brushes are used to prevent damage to fragile brick facings and mortar.  If left, the creosote can ignite and cause a chimney fire.  This is where chemical treatment is required.

If you are thinking of installing a stove in an existing chimney, your installer may ask you to arrange chemical cleaning of your flue prior to fitting a stainless steel liner.  This is because any creosote in the flue can still ignite after the chimney is lined.  Treatment will also prevent unsightly staining of the interior walls of the house though tar seeping through the porous brickwork and plaster.


The chemical agents change the creosote into a brittle substance which is more easily removed with brushes.  It consists of four components:

  • A reactive agent neutralises the acidic creosote making it less corrosive and less flammable

  • A dehydrator absorbs the oils and moisture

  • A combustion inhibitor helps reduce the chance of a chimney fire

  • A magnesium catalyst breaks down the creosote when heated by normal use

Treatment should be carried out during the burning season because the chemicals are heat-activated.  


The chemical is in the form of a powder and it is applied directly into the chimney using an applicator and air compressor.  To ensure a positive air-flow, the flue will be heated with either an electric heater or a small fire.  The nozzle of the applicator is pointed directly into the chimney in the direction of air flow and the chimney is coated in a generous layer of powder.  Once treated, the householder will need to light a fire for a minimum of two hours each day for two days, and then at least every other day for 1-2 weeks.  After this time, the chimney can be swept again as normal to remove the residue and the modified creosote.