Abstract: At approximately 7:30 a.m. on September 24, 2008, Employee #1, the Night Shift Supervisor, was discovered unresponsive at the bottom of the tank of a tanker truck. Hydrogen sulfide gas levels of 60 parts per million to 200 parts per million were detected in the tank by the Fire Department. Employee #1 was working at a nonunion, recycling operation where they collect used cooking oils and greases from oil water separators and other reservoirs at restaurants and food production facilities and process these waste materials for resale as various animal feed product additives. Employee #1 was cleaning the inside of one of the tanker trailers that had been used to collect waste cooking oils and greases mixed with water. The tanker was not draining properly and spraying water into the tank from the open hatch was not effective so Employee #1 climbed through the 20-in. wide access hatch at the top of the 40- ft long, 6,500 gallon tanker. Employee #1 was asphyxiated and was hospitalized as an inpatient for five days.