Abstract: At approximately 12:30 a.m. on August 26, 1990, employees in the finishing department detected an unusual odor. The supervisor was notified and the area was investigated by the Du Pont recovery operator. What was thought to be the problem was corrected by turning water back on to the acrylonitrite vent scrubber system. The odor was undetectable about 1:30 a.m. but returned about 3:00 a.m. All employees in the department were given dust masks. The team leader was notified of the odor about 3:30 a.m. and the recovery operator again investigated. A leak was detected coming from a decanter. The recovery operator stopped the leak and decontaminated the area. Blockage in the monomer distillation column caused acrylonitrite to back up in the vent system of the decanter. Fumes were brought into the plant through the HVAC system. Between 4:00 and 5:00 a.m., the odor was noticeable in the hallways and bathrooms. Employee #10 had a headache; Employee #11 was faint, had trouble breathing, and had a rapid heart rate. Please note that Employees #10 and #11 were contracted by Du Pont to work in the finishing department. Employee #7 was vomiting and was experiencing burning of the eyes, chest, and throat; Employee #8 was experiencing burning of the throat and chest. At 5:15 a.m., the employees were told to leave the area; they went to the cafeteria. EMTs arrived at the site by 6:00 a.m. and transported Employees #1 through #11 to Kershaw County Memorial Hospital. Blood oxygen content tests, routine blood work, and chest x-rays were conducted. All the employees were released except for Employee #8, who was transported to Richland Memorial Hospital due to the low oxygen content in his blood. The hospital saturated Employee #8 with oxygen, kept him overnight for observation, performed a chest x-ray and pulmonary function test, and then released him. The highest level of acrylonitrite was measured at 12 ppm in the acrylonitrite recovery area.