Air Quality

California’s Smog Check Program is a critical part of the state’s clean air strategy and helps improve the air we breathe every day.

The smog released by vehicles contains pollutants which react chemically in the presence of sunlight and can harm our health. Thanks to California’s smog check program, approximately 400 tons of these smog-forming emissions are removed from California’s air each day. A regular smog check will ensure that fewer of these damaging pollutants are released and that our air will be fresh and safe to breathe for all Californians. 

Contribute to improving air quality by taking care of any issues identified during your vehicle’s Smog Check.

Quick facts

  • Smog pollutants irritate the respiratory system, reduce lung function, aggravate asthma, and damage the lining of the lungs
  • Children, people who are active outdoors, and people who already have respiratory diseases are especially at risk
  • A study from Brigham Young University found that air pollution can shorten a person’s average lifespan by 1-3 years
  • Urban outdoor air pollution is the cause of an estimated 1.3 million deaths worldwide per year

Smog Check Milestones

  • 1943: The first widely reported smog incident occurs in Los Angeles. Frightened residents mistake the mysterious smog for a chemical attack.
  • 1950s: California’s Public Health division studies the causes of smog, where it forms, and its effects on the body.
  • 1975: First vehicles to require catalytic converters for controlling pollution.
  • 1984: The first “Smog Check” program is created in California.
  • 1994: AB 2018 establishes an emissions inspection program, which later becomes the blueprint for the modern smog check.
  • 2009: Air Resources Board adopts the Low Carbon Fuel Standard, aiming to reduce emissions by 16 million metric tons by 2020.
  • 2010: AB 2289 introduces extensive reforms to the Smog Check Program through simplifying inspection procedures for newer vehicles.

Tips for maintaining your vehicle and reducing pollution:

  • Use the proper tire size, rotate and align tires frequently, and check your tire pressure often
  • Use the correct fuel octane and don’t top off at the gas pump
  • Follow the manufacturer’s recommendations for changing your oil and use the proper grade and quality
  • Check your oil levels often and repair any leaks as soon as you find them.
  • Don’t ignore dashboard indicator lights such as the check engine light
  • Get vehicle repairs at licensed stations


Air Now: Check your region’s current Air Quality Index.

Air Resources BoardLearn how you can help promote clean air in California.

State of the AirLook up current and historical State of the Air reports by county.