This is because there is smoke coming back into your room probably bringing carbon monoxide with it. There are 4 main causes:
- The fireplace is too large for the flue. The best solution is to reduce the size of the opening.
- The chimney pot/terminal is too small (narrow). Ensure that the flow of the flue gasses is not inhibited in any way. A narrow pot can cause an obstruction. Make sure that the chimney pot is the correct size for the internal flue.
- The flue is partially blocked (sooty deposits, birds nest, partial collapse). Call us to immediately to remove the obstruction and clean the flue.
- Down-draughts can also cause smoke marks, see the section on Down Draughts on the Chimney Problems page.