Significance

• Vehicles emit air pollutants. When vehicles are tested at specified intervals, the air in the places where smog certification is required stays cleaner. California licenses automotive service stations or car repair shops to conduct the tests and inspect the vehicles.
  
  

Considerations

• The state tests for carbon monoxide, hydrocarbons and nitric oxide. Inspectors check the tailpipe, the gas cap and the catalytic converter to make sure that the equipment is intact. Areas that are prone to high air pollution because of their topography have higher standards for emissions than areas with lower levels of pollution. The state requires smog checks each time a vehicle changes ownership, although new vehicles shipped to California are exempt from this requirement.
  
  

Benefits

• The state has reduced its air pollution load considerably by licensing only vehicles that burn clean. Since 1966, when California enacted the emission testing requirements, the air in its metro areas has improved significantly. According to an article published in the L.A. Times, as of 2008, vehicles in California emitted 1 percent of the air pollution they did in 1960.