There are a few good reasons for getting your chimney swept. A clean chimney can protect your health. Breathing in fumes from gas or solid fuels can cause you serious damage. Cleaning your chimney ensures that the flue is clear allowing dangerous fumes to leave safely through the chimney.
Having your chimney swept will reduce the chances of chimney fires that can damage your chimney. Getting it swept will also avoid smoke damage to your room. If the fumes can't leave through your chimney it will enter your room which can damage decoration around your fireplace.