A smog check is part of a long-term plan to reduce air pollution and improve the air quality in cities around the country. Since the turn of the millennium, lots of people have suffered from the harmful effects of smog. Thousands of children and seniors got respiratory illnesses because of exposure to smog. The components of smog include carbon monoxide, sulfur oxide, nitrogen oxide and ozone. These chemicals are toxic and cause not only health ill effects but all bad effects on the economy.