California smog check areas by county and ZIP code

The short answer

California has 58 counties. DMV lists 34 of them as biennial for the whole county, which means a smog check every other year at renewal. It lists six more as biennial in certain ZIP codes only. The other 18 counties are not on either DMV list. The full county table and every partial county ZIP code are below.

The three program areas

BAR splits the state into three program areas based on air quality. Enhanced areas do not meet federal or state standards for ozone and carbon monoxide. Basic areas have cleaner air that is still marginal. Change of ownership areas are rural, and a smog check shows up only when you sell a car or first register it. State law lets the enhanced program run only in urban areas with serious, severe or extreme ozone problems, or with moderate or serious carbon monoxide problems.

BAR's data uses a fourth label, "Partial Enhanced." BAR reports its stations and tests under that label too.

In enhanced areas, a share of cars are sent to STAR stations, which hold higher performance standards. See our STAR station guide for how that works.

Full county list

This table puts all 58 counties in one place. The first two groups come straight from DMV's smog inspection page. The third group is every county that DMV does not list.

Counties with biennial checks for the whole county

These 34 counties are on DMV's list. A smog check is part of renewal every other year once your car is old enough. Los Angeles is on the list with one exception, ZIP code 90704.

Counties on only part of the list

El Dorado, Placer, Riverside, San Bernardino, San Diego and Sonoma need biennial checks only in the ZIP codes listed below. Cars registered in other ZIP codes of these counties are not on the biennial schedule.

Counties DMV does not list

These 18 counties are not on either DMV list. BAR's change of ownership program covers rural areas, so a smog check there comes up mainly at a sale or a first registration. Call DMV or the DCA Consumer Information Center at (800) 952-5210 if you want a confirmation for your address.

Catalina Island

Avalon, ZIP code 90704, is exempt from smog requirements under Health and Safety Code section 44044. It is the only exempt ZIP code in Los Angeles County.

Every ZIP code in the six partial counties

DMV publishes a list of ZIP codes in the six partial counties. We expanded the ranges into single ZIP codes. That gives 517 ZIP codes in all.

DMV's page was last revised in November 2011, and expanding ranges can add a few ZIP codes that are not in use. If your ZIP code is missing, check with DMV before you assume you are exempt.

Together these ZIP codes held 7.2 million registered vehicles at the end of 2024, which is 23 percent of the 31.1 million vehicles in the state. Riverside and San Diego carry most of the weight.

Find your county below, then scan for your ZIP code. On a computer you can use Ctrl+F or Command+F to search the page.

El Dorado County

Placer County

Riverside County

San Bernardino County

San Diego County

Sonoma County

What the data shows about each area

BAR counts stations and tests by program area. The enhanced areas do most of the work. About 86 percent of initial tests in 2025 happened there.

The numbers show a few things. Enhanced areas hold 6,099 of the 7,329 licensed stations. Basic areas hold 743, partial enhanced areas 380, and change of ownership areas just 107. Fail rates for newer cars are close to 8 percent in every area. The bigger gap is in the older cars. The 1999 and older group fails 14.3 percent of first tests in basic areas and about 18 to 20 percent in the enhanced and partial enhanced areas.

Why some counties sit in more than one area

A county does not have to fall in one program area. BAR places an address in an area by ZIP code, so a single county can hold two or even three areas. This is why DMV lists six counties by ZIP code. It is also why a car can be tested differently from one in the next town over.

The area sticks to the registration record. If you move across a county line, or only across a ZIP boundary, update your address with DMV. The station works from the address on file. When the file is out of date, the station may be unable to start the test. BAR keeps a zip update page for this, and the DCA Consumer Information Center answers at (800) 952-5210.

State law sets the outer edge of the enhanced program. It can run only in urban areas that EPA classes as serious, severe or extreme for ozone, or moderate or serious for carbon monoxide with a design value over 12.7 parts per million. Health and Safety Code section 44010.5(e) says so.

How busy the stations are

Stations in the enhanced areas handle the most cars each. The enhanced areas averaged about 1,592 initial tests per licensed station in 2025. Change of ownership areas averaged about 646. That follows from how the program works. Biennial areas send every aging car through a station every two years. Rural areas only see a car when it is sold or newly registered.

For drivers the point is practical. In the busy areas, plan ahead and use the 90 day window. You can test up to 90 days before the due date. In rural areas there are fewer stations, so call first. Our station finder shows what is close to you.

How to find your area

1. Find your county. Use the table above.
2. If the county is partial, find your ZIP code. Use the lists above.
3. Read your renewal notice. If it says "Smog Certification Required," you need a check for this renewal.
4. Check your DMV address. If DMV shows an old address, a station may not be able to test your car. Use BAR's zip update page or call (800) 952-5210.
5. Find a station. Use the station finder or browse stations by county.

Still unsure the rules apply to your car? Read do I need a smog check. If your car is brand new, the model year lookup shows when your first check is due.