In embodiments, a control system for a UV air treatment system, especially one used for cleaning a fume stream such as in a kitchen exhaust system, detects a need for cleaning maintenance on the UV light source based on changes in light intensity. The system further detects the light intensity each time the UV light source is cleaned to determine if the drop in intensity after cleaning indicates that the UV light source should be replaced. The cleaning and replacement requirements are indicated automatically by a user interface.