Chimney residue is the collective term for the substances that accumulate in a chimney due to the burning of fuel. This residue includes ASH, SOOT, and FLUE, which are all byproducts of combustion. ASH is the solid remains of fuel after it has been burned, while SOOT is the fine black powder that is created when fuel is incompletely burned. FLUE is the gas that is produced when fuel is burned, and it is usually composed of carbon dioxide and water vapor. The final chimney residue is SWEEP, which is the name given to the person who cleans out the chimney.