Soot (IPA: /ˈsʊt/) is a general term that refers to the black, impure carbon particles resulting from the incomplete combustion of a hyrocarbon. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres, charred wood, petroleum coke, etc. that may become airborne during pyrolysis and which are more properly identified as cokes or chars. The gas-phase soots contain polycyclic aromatic hydrocarbons (PAHs). The PAHs in soot are known mutagens and probable human carcinogens. They are classified as a "Known Human Carcinogen" by the International Agency for Research on Cancer (IARC).