Sweeping must be done by a qualified professional who will issue a certificate confirming the flue has been cleared along its entire length.
There are two chimney sweeping methods:
From above
The chimney sweep will need to remove the chimney cap and insert the brush for a few metres: they will clean the blocked areas, then work their way down the flue.
From below
The chimney sweep will insert the brush mounted on one or two rods, cleaning the lower flue with several back-and-forth movements, adding rods to reach the top.
