California Code, Health and Safety Code - HSC § 40410.5

(1) When emission offsets are required to mitigate the air quality impacts of a stationary source, the offsets shall be secured by the applicant so as to bring about ambient air quality improvements within the sensitive zone. The applicant shall be required to demonstrate, to the satisfaction of the south coast district, that any emissions reductions acquired from stationary sources operating within the South Coast Air Basin will result in a demonstrable net ambient air quality improvement within the sensitive zone.

(2) In considering an application for a permit to construct or operate a stationary source, the south coast district board shall, in addition to making a finding and determination that the impacts of the stationary source will be mitigated so as to result in a net improvement in ambient air quality within the South Coast Air Basin, also make a finding and determination that the impacts of the stationary source can be mitigated so as to result in a net improvement in ambient air quality within the sensitive zone.