Abstract: At approximately 7:30 a.m. on July 23, 1991, Employee #1, of Domtar Gypsum, Inc., was cleaning a filler chest approximately 10 ft deep by 8 ft wide by 16 ft long (a confined space) using recycled water from a 100,000 gallon pit. At about 8:00 a.m., a coworker found Employee #1 in a prone position inside the filler chest. The coworker entered the chest to assist Employee #1, but was unsuccessful. He exited the filler chest and went to get help. The coworker told a supervisor, who then instructed Employees #2 and #3 to enter the chest and help Employee #1. As Employees #2 and #3 were moving Employee #1 to a position closer to the ladder, they felt weak and collapsed. Paramedics removed all three bodies from the filler chest and transported them to a hospital. Employee #1 was killed; Employees #2 and #3 were hospitalized. Subsequent tests showed that the filler chest was contaminated with hydrogen sulfide gas, which apparently came from the water in the 100,000 gallon pit.