Creosote is the result of the distillation of tar, which is a by-product of combustion in many solid fuels. There are three stages or degrees of creosote.
Third degree creosote is a tough problem to deal with, and it’s not unusual for people to replace their flue liners in order to get rid of it. This kind of creosote can look like tar running down the inside of your chimney or a shiny glaze coating the inside your stove or flue.
It is a highly concentrated fuel which hardens and can form a thick layer. As such it can easily catch fire resulting in a potentially devastating chimney fire.
Third degree creosote cannot be removed by conventional sweeping using a brush. It must be chemically treated and then swept using a rotary chain or wire flail. It may take several treatments to completely remove it.
Third degree creosote is usually the result of one or more of the following:
- Incomplete combustion
- The chimney is not insulated or is cold for some other reason
- Unseasoned wood is being burned
- Insufficient ventilation to the room.
- An oversized flue
If you suspect that Third Degree Creosote is present in your flue you should contact a professional and registered chimney sweep to have it assessed.
Remember this is a highly flammable substance.
Some examples of flues which have become contaminated with 3rd degree creosote
How does it work?
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. A combustion inhibitor helps to reduce the chance of a chimney fire.
Finally, a magnesium catalyst helps break down the third degree creosote when the flue is heated during normal use.
The net effect is that the creosote is converted to a more brittle state that has different expansion and contraction rates than the flue to which it is attached, as a result of the heating and cooling cycles it becomes loose and begins to detach from the flue.