Q. What is creosote?

A. Creosote is a flammable and corrosive substance that can build up on the walls of your fireplace and chimney. Creosote forms when unburned wood particles, fly ash and other volatile gasses combine as they exit the chimney. If there’s a poor draft, these unburned particles and gasses can condense and build up on the walls of your chimney. Over time, these build ups can become a danger as they can potentially result in a chimney fire.

Q. What are the different stages of creosote development in chimneys and stoves?

A. There are usually 4 stages, and there are different treatments for particular stages:

Stage 1 – Condensation:

In an attempt to save fuel, many people reduce the amount of air entering the combustion chamber, causing the appliance to smoulder, with serious side effects. Smoke then cools as it rises in the chimney, not having enough heat energy to escape the stack. The flue gas then condenses on the inside of the chimney and the sap/resin turns into creosote. This swollen creosote is very fragile and brittle. It can block the flue and cause tremendous smoking problems.

Stage 2 – Liquidation:

This sap/resin turns liquid and can seep into mortar joints or cracks in the flue tiles. The corrosive property held by creosote destroys masonry work and jeopardizes the life of your chimney.

Stage 3 – Solidification:

As temperatures fall and rise within the chimney, causing the heating and cooling of the creosote. This quickly enables build-up, reducing the amount of space the flue gas has to exit the chimney and, in extreme cases, blocking the flue completely. This build up can look like tar and is frequently termed “tar build-up.

Stage 4 – Fragile State Creosote:

When the solid creosote is burned, all volatile oils are removed leaving a residue that appears very similar to honeycomb which is crisp and easy to sweep from chimneys.

Q. What Is Creosote Glazing

A. Glaze forms in the solidification stage and occurs when new layers of creosote build so quickly that the layers below it have no time to dry. These fresh layers then insulate previous deposits so it eventually solidifies creating the rock-like substance known as glaze.

CCTV Chimney Inspections

Q. When should I consider having a chimney CCTV inspection survey?

A. There are actually several occasions when you should do so:

  1. After a chimney fire.
  2. If you’ve moved into a new house and want to know the condition of the flue.
  3. If you are changing the heating appliance that the flue serves (e.g. if you’re having a new stove fitted).
  4. If you are experiencing chimney problems such as the smell of smoke in a room upstairs or in any other room when the fire is going.
  5. If there are cracks or smoke spillage marks on the walls surrounding the chimney breast or stack.