The term 'SWEEP SPOTS' can be solved by the four letter word 'SOOT'. SOOT is a black or dark gray powdery or flaky substance consisting mainly of amorphous carbon, produced by the incomplete combustion of coal, oil, wood, or other organic matter. It is often found in chimneys and is a common by-product of burning fossil fuels. SOOT is also a major component of air pollution and can cause respiratory problems in humans.