Over time chimneys can become blocked for many reasons e.g. soot, debris from birds, cobwebs etc. 
If left untreated this can cause fires, breathing difficulties for homeowners, stained furnishings and more importantly  introducing poisonous gases like Carbon Monoxide into the living area. Carbon Monoxide is completely odourless and cannot be detected other than by a detector.  If left untreated it can render the the occupants unconscious and possible fatalities
Combined with water vapour you can also produce acids into the exhaust area which will attack the brickwork.
Nigel Bartlett has been an experienced chimney sweep for many years and as well as clearing the problem he can advice on the best way to get maximum efficiency from your system.
Nigel uses both conventional and electric cleaning techniques, and can implement waterproofing methods as well as advising on corrosion in the brickwork. We also fit soot boxes for easy access.