Chimney powder, also known as SOOT, is a fine black powdery substance that is produced when fuel is burned. It is composed of tiny particles of ash, tar, and other materials that are released into the air when fuel is burned. Chimney powder is often used to clean chimneys and other areas where smoke and SOOT accumulate. It is also used in fireplaces and wood-burning stoves to reduce the amount of smoke and SOOT produced.