Abstract: Between 8:00 a.m. and 9:30 a.m. on December 2, 1988, employees at the Allstate Insurance Company building in Irving, Texas were exposed to an unknown gas or gases. At approximately 8:00 a.m., a large diesel truck and a bobtail truck pulled up to the building's loading docks, which were located 50 ft or less below the fresh air intakes for the third-floor heating, ventilation, and air conditioning system. At about 8:30 a.m., Employee #1 detected an odor on the third floor and began to feel nauseated and dizzy; she fainted within a few minutes. Soon after Employee #1 became ill, other employees on the third floor also began to feel sick. The Fire Department arrived before 9:00 a.m. and started to evacuate the building. Between 9:00 a.m. and 9:30 a.m., as the building was being evacuated, more people began to feel ill. Employees #2 through #10, along with many others, were taken to local hospitals by ambulance or bus. Apparently, 65 employees were taken to hospitals. However, only 10 of them were listed on injury lines on the original form.