Smog Check Basics

Smog checks are designed to ensure the amount and type of pollutants your vehicle is emitting do not exceed maximum standards.

There are multiple components of any smog test, and your vehicle must pass all parts of the test to pass. 

  1. Visual inspection of emissions control components and systems.
  2. Functional inspection of the vehicle’s check engine light, ignition timing, exhaust gas recirculation system, fuel evaporative system, and visible smoke.
  3. Functional inspection of the vehicle’s On-Board Diagnostic (OBD) system.
  4. Tailpipe emissions inspection.

*Some vehicles are not subject to all of the above test components.

After the inspection, you will receive a copy of the Vehicle Inspection Report (VIR), which shows the test results. If your vehicle passes, you will receive a certificate of compliance.

Types of smog check stations

The majority of Californians can have their vehicle Smog Check performed by industry. Smog Check Referee stations were created to perform more complex smog inspections and handle special smog check circumstances that industry is not authorized to provide. Again, most vehicles can be tested at Smog Check stations in the industry. There are several different types of stations to choose from, depending on your situation:

  • STAR stations meet higher standards and are more closely monitored by the Bureau of Automotive Repair. Certain types of vehicles may be required by the DMV to be tested at a STAR station. 
  • Test-Only stations specialize in smog inspections and are not permitted to perform diagnostics or repairs. The DMV requires certain vehicles to be inspected at test-only facilities. If the vehicle fails at a Test-Only station, the consumer can then take the vehicle to a qualified Test-and-Repair or Repair-Only station of their choice.
  • Test-and-Repair stations are authorized to perform smog inspections, diagnostics, and repairs. 
  • Repair-Only stations can diagnose and repair vehicles, but are not permitted to do any testing.  


For the most up-to-date information on smog check process, laws and station types, visit the Bureau of Automotive Repair.

To find a smog check station near you, use the Bureau of Automotive Repair station locator.