Abstract: On September 4, 1999, there was an unplanned plant-wide power failure at the facility where Employees #1 and #2 worked. As a result, the #4 dryer at the plant's hydro unit started to decompose. Workers tried unsuccessfully to control the decomposition by flooding the dryer with water. Employees #1 and #2, both control room operators, entered the control room, apparently to reset some fans in anticipation of the power being turned back on. Assuming that the control room was a safe haven, they removed their SCBAs. When the power came back on, sulfur dioxide gases and some hydrogen sulfide entered the control room via the air conditioning and Purafil systems, whose duct works had holes. The two men were overcome by the fumes. Employee #1 died and Employee #2 was hospitalized. He could not speak and had lost control of his extremities, although he apparently understood what was going on and could nod yes and no.