Numerous states besides California require that new cars must meet California emissions standards. This potentially impacts every owner and buyer of new or late model used cars as well as the DIYers and professional mechanics that work on them.

Below are answers to some of the most common questions:

• Are there still US federal emissions standards? Yes, states can choose to specify cars either meet Federal/EPA or California (CARB) emissions standards specifications. The emissions standards usually vary by model year, so check your state's emissions guidelines.
  
• How can I tell if a car is a California spec car? Look at the VEHICLE EMISSION CONTROL INFORMATION label clearly displayed in the engine compartment. It meets California emissions specs if the label says “California emission standard (CARB certified)”, “sale in all 50 states (50-state certified)”, or “sale in the northeast”. The VEHICLE EMISSION CONTROL INFORMATION label is also where you will find "Engine Family" or "EFN" numbers.
  
• I do not live in California or one of those emissions states so why do I care? Used cars from the California spec states could show up for sale in any state. New states are steadily joining the California spec list. If the car is a California spec car then it might eventually need California spec replacement parts or service.
• Why are some of the replacement catalytic converters listed in the RockAuto.com parts catalog described as being for California emissions equipped models but “not legal for sale on vehicles licensed in the state of California?” Since January 1, 2009, California requires that aftermarket catalytic converters sold in California have special California Air Resource Board (CARB) certification and labeling. An exhaust manufacturer may have built a catalytic converter that meets or exceeds California emissions standards, but they have not yet received CARB certification so their catalytic converter cannot be sold in California.
  
• If a catalytic converter meets California emissions standards but does not have CARB certification then can it still successfully be installed on California spec cars outside California? Yes.
  
• I live in California. Will a new (manufactured after January 1, 2009) catalytic converter that meets California emissions standards but does not have CARB certification still enable my car to pass state emissions tests? No. The catalytic converter meets California emissions standards so the vehicle’s exhaust will likely pass emissions tests. But the vehicle should still fail because the test includes a visual inspection of the exhaust system. CARB certification requires special CARB numbers be stamped into the body of the catalytic converter. Without the CARB label on the new aftermarket catalytic converter, the state inspector will fail the car no matter how clean the exhaust is. Catalytic converters made before 2009 or newer ones without CARB certification still have a date of manufacture stamped on them per Federal/EPA requirements.
  
• Will this get less or more complicated in the future? It might get less complicated if the California emissions standards are adopted by all the states or if car manufacturers decide to only make California spec cars. But it could get more complicated if other states besides California are allowed to come up with their own emissions standards or if California or other states write new regulations similar to the CARB certification for replacement catalytic converters.