California Customer:

California laws specifically prohibit the use of any aftermarket product whose installation requires the removal of any emissions control related components. These laws are regulated by the California Air Resources Board ( )

The Air Resource Board has established three classifications of emissions related aftermarket products which define which aftermarket parts can be sold legally in the state of California:

  1. “Replacement Parts” – parts that have the same function and effect on emissions as the parts they are replacing. This means that if a vehicle was not originally equipped with a catalyst and all other emissions related controls that were connected like oxygen sensors are reconnected, then the part is considered a Replacement Part. If the vehicle does have a catalyst and the installation of the part does NOT remove the catalyst (ie. cat back system) and all other emissions related controls are reconnected, then this is also considered a replacement part. Slip on mufflers in applications where the catalyst is not contained in the original muffler are an example of a replacement part. Full system exhausts when installed on vehicles that did not originally contain a catalyst and whose design allows the reinstallation and original function of any other emissions control related components are also considered replacement parts.
  2. “Air Cleaner” Most emission controlled vehicles will have an air cleaner that is a closed element type or thermostatically controlled. A replacement air cleaner must meet the same specifications as the original and connect to any emissions equipment that was attached to the original equipment air cleaner. Any replacement air cleaner elements may be used as long as they meet original factory specifications. Any air cleaner that does not meet the original factory specifications requires an Executive Order to be legal for street use.
  3. “Modified Parts” – parts that alter the emissions control related performance from the original part they are replacing, These parts may have catalysts in them but they perform differently from the original equipment part or they may require the alteration or elimination of other emissions related control components such as oxygen sensors. These parts must obtain an Executive Order from the Air Resource board to confirm their functional compliance in order to be sold legally in California.
  4. “Competition or Racing Vehicle Parts” – parts that are used exclusively in competition on race only vehicles. These parts do not require approval as long as they “are not used on public highways”.
    Labeling a product as being for “Racing Only” or “Closed Course Competition” is not sufficient for it to be included under this classification. It must be a competition vehicle and must not be used
    at any time on a public highway.

This document is a summary interpretation. For additional information, please contact us or visit the following link:


I have been informed of the laws and regulations regarding emissions control related components installation and use in the state of California.