Industrial smog characterized by high ambient concentrations of sulfur dioxide (${\text{SO}}_2$) and smoke particles is commonly known as:

Classical or reducing smog, which results from burning large quantities of sulfur-bearing coal, is historically termed London smog due to the catastrophic 1952 air pollution incident. Photochemical smog, on the other hand, is rich in ozone and hydrocarbons and is referred to as Los Angeles smog.