Abstract: At approximately 8:00 a.m. on August 26, 2008, Employee #1 retrieved one load of nonhazardous industrial sludge from a chemical facility with a vacuum tanker truck. Nearby coworkers noted that Employee #1 had observed that the volume gauge on the side of the tank was not working properly and that there was probably a problem with the float ball in the tank. Employee #1 delivered the sludge to the city wastewater treatment plant and returned to his shop to repair the tank. At approximately 9:18 a.m., Employee #1 asked Employee #2 to watch him enter the tank. Employee #1 opened the upper hatch of the tank, commented that there was a strong smell and entered the tank. Employee #2 heard no noises from Employee #1, climbed onto the tank approximately one minute after Employee #1's entry and observed Employee #1 collapsed at the bottom of the tank. Employee #2 called for assistance, entered the tank, and attempted to pass Employee #1 to two coworkers on top of the tank. Employee #2 lost consciousness and the two coworkers released Employee #1. Emergency services arrived within six minutes and took the two employees to the hospital. Employee #1 remained on life support until his death at approximately 10:30 p.m. on August 27, 2008. Employee #2 remained on life support until he regained consciousness on the afternoon on August 27, 2008; he was released on August 30, 2008.