Abstract: On August 3, 2011 Employee #1, a contractor, was installing a sanitary sewer line. At approximately 4:21 p.m., a coworker opened a manhole cover to measure the depth of the main sewer line. Employee #1 was exposed to the toxic atmosphere, lost consciousness, and fell through the manhole approximately 21 ft to the bottom of the pit. At the bottom of the pit was approximately 10 in. of sewage and water. The coworker immediately entered the manhole without testing the atmosphere to try to rescue Employee #1. While climbing down the pit ladder, the coworker also lost consciousness and fell approximately 16 ft to the bottom of the pit. Emergency responders were summoned. A police officer and a civilian passerby entered the pit to rescue Employee #1 and his coworker. When they experienced the same conditions, they exited the manhole. Additional emergency personnel rescued Employee #1 and his coworker. Employee #1 was found unresponsive, lying face-down in the sewage and water, with a head contusion. He was transported to a hospital and later pronounced dead. The coworker was responsive and made a full recovery.