Health and Safety Code § 42702
CHAPTER 5. Monitoring Devices
The state board shall specify the types of stationary sources, processes, and the contaminants, or combinations thereof, for which a monitoring device is available, technologically feasible, and economically reasonable. Such specification may be by any technologically based classification, including on an industrywide basis or by individual stationary source, by air basin, by district, or any other reasonable classification.