Smog is a mixture of smoke & fog.
Two types of smog.
1. Classical smog: It is mixture of smoke, fog & SO2. It occurs in cold humid places. It is also called reducing smog because it contains reducing mixture.
2. Photochemical smog: This type of smog results from the action of sunlight on the nitrogen oxides & hydrocarbons produced by automobiles & factories. It is called oxidizing smog because it contains oxidizing mixture.
