An unswept flue can lead to poor combustion of your solid fuel resulting in at the very least an inefficient method of heating your home. In worst case scenarios it may also lead to chimney fire or Carbon Monoxide poisoning.
http://www.becarbonmonoxideaware.com/index.html

A chimney needs to be swept because it is an exhaust system for your heating appliance. Having your chimney swept by a professional reduces the build up of tar and other deposits which form on the internal walls of the flue way (generally caused as a result of incomplete combustion of the fuels used) and also to ensure that the flue way has not been partially or completely blocked as a result of debris falling down the chimney (generally caused by birds nesting or tiles, slates or masonry falling down the chimney stack).

As soot is classified as a hazardous product (it contains cancerous carcinogens) we use a state-of-the-art HEPA filter Numatic vacuum with a 99.997% filtration efficiency.