Soot is a mass of impure
carbon particles resulting from the incomplete combustion of
hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual
pyrolysed fuel particles such as
coal,
cenospheres, charred wood, and
petroleum coke that may become airborne during
pyrolysis and that are more properly identified as
cokes or
chars.