The University of Pennsylvania does not require UV lights in biosafety cabinets. The Biosafety in Microbiological and Biomedical Laboratories, 5th Ed (Appendix A, Section VI), states the following:
Ultraviolet Lamps
“Ultraviolet (UV) lamps are not required in BSCs nor are they necessary. If installed, UV lamps must be cleaned weekly to remove any dust and dirt that may block the germicidal effectiveness of the ultraviolet light. The lamps should be checked weekly with a UV meter to ensure that the appropriate intensity of UV light is being emitted. UV lamps must be turned off when the room is occupied to protect eyes and skin from UV exposure, which can burn the cornea and cause skin cancer. If the cabinet has a sliding sash, close the sash when operating the UV lamp.” (http://www.cdc.gov/od/ohs/biosfty/bmbl5/BMBL_5th_Edition.pdf)