was with vacuum cleaners and mopping. Workers wore white lintless gloves. At the peak of construction activity in May 1945, 25,266 people were employed on the site. Other buildings Although by far the largest, the main process building (K-300) was but one of many that made up the facility. There was a conditioning building (K-1401), where piping and equipment were cleaned prior to installation. A feed purification building (K-101), was built to remove impurities from the uranium hexafluoride, but never operated as such because the suppliers provided feed good enough to be fed into the gaseous diffusion process. The three-story surge and waste removal building (K-601) processed the "tail" stream of depleted uranium hexafluoride. The air conditioning building (K-1401) provided per minute of clean, dry air. K-1201 compressed the air. The nitrogen plant (K-1408) provided gas for use as a pump sealant and to protect equipment from moist air. The fluorine generating plant (K-1300) generated, bottled and stored fluorine. It had not been in great demand before the war, and Kellex and the Manhattan District considered four different processes for large-scale production. A process developed by the Hooker Chemical Company was chosen. Owing to the hazardous nature of fluorine, it was decided that shipping it across the United States was inadvisable, and it should be manufactured on site at the Clinton Engineer Works. Two pump houses (K-801 and K-802) and two cooling towers (H-801 and H-802) provided of cooling water per day for the motors and compressors. The administration building (K-1001) provided of office space. A laboratory building (K-1401) contained facilities for testing and analyzing feed and product. Five drum warehouses (K-1025-A to -E) had of floor space to store drums of uranium hexafluoride. Originally this was on the K-27 site. The buildings were moved on a truck to make way for K-27. There were also warehouses for general stores (K-1035), spare parts (K-1036) and equipment (K-1037). A cafeteria (K-1002) provided meal facilities, including a segregated lunch room for African Americans. There were three changing houses (K-1008-A, B and C), a dispensary (K-1003), an instrument repair building (K-1024), and a fire station (K-1021). In mid-January 1945, Kellex proposed an extension to K-25 to allow product enrichment of up to 85 percent. Grove initially approved this, but later canceled it in favor of a 540-stage side feed unit, which became known as K-27, which could process a slightly enriched product. This