Research laboratories engaged in scientific investigation, testing or the production of factual information for industrial, commercial or institutional clients, where no physical or tangible product for general marketing is directly produced therein, and provided that the Board of Supervisors determines that no potential danger, hazard or nuisance shall exist to the employees, building occupants or surrounding areas, and provided that the Board of Supervisors determines that no waste other than normal domestic sewage is discharged into any sewage disposal system. Chemical or biochemical research, however, is specifically prohibited [§ 185-38E(1)].