Sulphur dioxide smog is known as:

Smog is classified into two main types based on its composition and formation:
* London Smog (Classical Smog): Occurs in cool, humid climates and is a reducing chemical mixture of smoke, fog, and sulphur dioxide (${\text{SO}}_2$) gas derived primarily from coal combustion.
* Los Angeles Smog (Photochemical Smog): Occurs in warm, dry, and sunny climates and is an oxidizing mixture formed by the action of sunlight on nitrogen oxides (${\text{NO}}_x$) and hydrocarbons.