Individuals who modify their vehicles to run on cleaner alternate fuels (E85, CNG, etc.) can qualify and apply to become smog exempt in any state
Example: Taking a stock car running on gasoline and modifying it to run on E85. To modify a vehicle to run on E85, it requires the individual to switch to a bigger intake, larger fuel injectors, larger fuel pump, extra sensors, and at times (depending on the vehicle) requires an ECU stand alone system to control the newly modify components. Doing this will fail the vehicle at smogging due to the visual inspection for multiple issues, one being that the vehicle doesn't have the OBD connection anymore. Even though the vehicle failed visually, out the tailpipe the vehicle can be considered a LEV (Low Emission Vehicle) or ZEV (Zero Emission Vehicle)