What are the different types of smog?

There are two types of smog. These are: Classical and Photochemical smog.
Classical smog occurs in cool humid climate. It is a mixture of smoke, fog and sulphur dioxide. It is also called a reducing smog.
Photochemical smog occurs in warm, dry and sunny climate. The main components of the photochemical smog result from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories. Photochemical smog is also called as oxidising smog.