Manufacturers of add-on and modified parts planning to sell their product for use in California vehicles should apply for an exemption from Vehicle Code Section (VC) 27156. A VC 27156 exemption is granted if the product has been determined not to cause any increase in vehicular emissions. The first step to obtain a VC 27156 exemption is to submit an application to the Air Resources Board.
Once the application has been filed, the Air Resources Board will usually contact you within three weeks to inform you of missing information or to specify test vehicles. You are responsible for obtaining the vehicles and having them tested at a qualified independent laboratory. If you have any questions concerning the suitability of a vehicle for testing or the test themselves, please contact the staff engineer assigned to your application. If confirmatory testing is required at the Air Resources Board's laboratory after you completed the testing, you must provide the test vehicle, but there is no charge for testing.
Manufacturers must present sufficient information to establish that an emissions increase will not result from the use of an add-on or modified part. If your device or modification is exempted, the Air Resources Board will issue an Executive Order stating that the part will not adversely affect emissions and that it is legal for sale and use in California.