If your car was made after 1998 and uses gasoline, then you will need a smog certification. Some states require a smog certificate every 6 months while others only require a certificate once a year or every other year. The first time you purchase a car, the seller will provide the smog certificate. Certain types of cars are exempt from such checks.
- Hybrids. Hybrids have both a combustion engine as well as an electric motor. If you have a hybrid electric car then you are only exempt from the change of ownership and first biennial smog check. The technology for testing this type of vehicle is currently being developed. Once it has been established then vehicles will be required to be tested.
- Models from 1975 or earlier. Previous laws stated that a car that was 30 years old or older was exempt. However this has been recently changed to any car made before 1975. This is mainly because most very old cars are classic vehicles and rarely driven. Additionally the parts and engines are old and cannot be modified for the current emission standards. Most cars manufactured before this date are not still on the road, so the majority of vehicles must meet emission and smog standards.
- Diesel cars from before 1998. Any diesel car from before 1998 is exempt, though there is a diesel smog test for newer diesel vehicles. This test does not use the normal emissions test from the tailpipe. This type of check is a visual inspection and a check of the on-board diagnostics. There is also an EVAP functional test. This visual test is a visible smoke test.
- Electric cars. Most electric cars are exempt because such vehicles have no tail pipe and produce no emissions. The department of motor vehicles has a growing list of electric vehicles that are exempt from smog certifications.
- Natural gas cars. Only small natural gas vehicles are exempt. This includes vehicles that are less than 14,000 pounds. These vehicles are only exempt for the first six years. This exemption is because the natural gas vehicles go through such strict testing to make it to the dealer that a smog test is irrelevant. After the six year period, the warranty is normally finished. The components of the vehicle could now possibly fail and they need to be checked.
- Other vehicles. Currently, motorcycles are exempt as the engine is not large enough. Other vehicles that are exempt include those that use two cylinders, rotary engines, off-highway vehicles, and two-cycle powered cars.