Chimney sweeps clean flues and chimneys to remove soot, tar and other deposits that build up when fires and heating appliances are used. This helps maintain a clear route for smoke and combustion gases to escape and can reduce the risk of chimney fires and carbon monoxide entering a building. Sweeps commonly work on open fires, wood-burning and multi-fuel stoves, and some other solid-fuel appliances. A visit may include checking the chimney or flue for blockages, damage or signs of poor ventilation, as well as sweeping with brushes and specialist vacuum equipment. Sweeps may use cameras or carry out smoke tests where appropriate, and can provide a record of the work or explain any problems found. Some also clear bird nests, fit bird guards or cowls, and undertake minor maintenance; significant repairs or appliance work may need a separate specialist. They can advise on how often a chimney should be swept, depending on the fuel, appliance and frequency of use.