The Smog Check program divides the state into three areas determined by the air quality in the designated area.
These areas, Enhanced, Basic, and Change of Ownership, may requiredifferent vehicle inspections,
inspection equipment and technician licenses. Generally, the area in which a station is located determines the
required station and technician license type and the station test equipment requirements. Likewise, the area in which
a vehicle is registered designates what type of inspection applies.
Smog Check certification is required in all program areas when an affected vehicle changes ownership,
with the exception of gasoline vehicles 4 or less model-years old.
For Basic and Enhanced Areas, a Smog Check inspection is also required biennially.
These areas do not meet federal or state air quality standards for ozone and carbon monoxide.
Biennial Smog Check inspections are required in these areas. Additionally, a portion of the vehicles in Enhanced Areas
must receive the biennial Smog Check at Test Only stations or special Test and Repair stations, known as Gold Shield.
In order to measure NOx emissions, most enhanced area vehicles are subject to a dynamometer loaded mode
Basic areas are less polluted then Enhanced Areas; however, due to their marginal air quality,
biennial inspections are required. Basic Area vehicles can receive biennial testing/certification at licensed
Test and Repair or Test Only stations. Basic Area vehicles are subject to a two speed idle test. Loaded mode tests
are not required in basic areas.
Change of Ownership Areas:
These more rural areas of the state require Smog Check testing only when a vehicle changes ownership or is
initially registered in California, except for vehicles 1975 model-years and older, and gasoline vehicles 4
or less model-years old.
Some counties are solely in one program area while other counties may have portions in two or three.