It's recommended by all official bodies and and associations of importance within the industry,
that chimneys are sweeped regularly, to prevent fires and keep the flue ways clear and safe to carry away the harmful fumes from the property in a safe manner.
This can be as regularly as once every:
3 months when in use when burning wood and coal.
At least ones a year for Gas, oil, smokeless fuels.
That is alot more often than most people realise.
So what happens to the flue over time,
when burning fuel, the chimney gathers small particles of soot that over time build up and clog the flue. This not only restricts the flue reducing the size but also is a fire risk and one small ember can set the chimney on fire. Why is this bad I hear you say, the chimney brickwork is dried in a kilns at 120°c and a chimney fire can reach 1800°c cracking the brickwork expanding and contracting the brick to such an extent, the chimney becomes unstable!
Also during a chimney fire, 25% of chimney fires migrate out side of a chimney leading to damage the rest of the building. Clean chimneys do not catch fire!
Now we know a little bit more about chimney fires, I hope you feel better about making the right decision.