There are two recognized types of smog, which are sulfurous smog and photochemical smog. Sulfurous smog is a high concentration of sulfur oxides in the air. Photochemical smog is nitrogen oxides and hydrocarbon vapors emitted by automobiles and other sources, which then undergo photochemical reactions in the lower atmosphere.
Smog is polluted air in a community. Sulfurous smog, which is also known as London smog is aggravated by dampness and a high concentration of suspended particulate matter in the air. Photochemical smog, which is also known as Los Angeles smog, does not require smoke or fog. It mostly occurs in urban areas that have a large numbers of cars.