California Code, Health and Safety Code - HSC § 44096

(a) The state board shall review and assess the potential cost-effectiveness, in terms of dollars per ton of emissions reduced, of emissions reduction devices that are intended for installation in light-duty motor vehicles and meet the qualifications specified in subdivision (b). The results of the assessment shall be made available to the department and the districts, and shall be considered by the state board in determining whether an emissions reduction device is a cost-effective means of emissions reduction, as compared with the accelerated light-duty vehicle retirement program conducted pursuant to Article 10 (commencing with Section 44100) and any other vehicle retirement program authorized by the department or the districts.

(b) The state board shall perform the review and assessment specified in subdivision (a) only for an emission reduction device that meets at least one of the following qualifications: