Abstract: On January 20, 2007, Employee #1 was working in the Hydrofluoric Acid, (HF), and Alkylation Unit in charge of maintaining the neutralization pits. He was in charge of draining a constant boiling mixture, (CBM's), which contained HF acid and water out of the polymer surge drum into a neutralization pit. The CBM's, low in pH, and were sent to the South neutralization pit to neutralize spent potassium hydroxide that was contained in the open-surfaced pit. Potassium hydroxide, (KOH), is highly basic and CBM's are drained into the South pit to lower or neutralize the pH. The draining of CBM's is accomplished by pressurizing the polymer surge drum with a constant supply of natural gas. The vessel is pressurized to 25 to 30 pounds and then a drain valve is manually opened and CBM's are forced out into the South neutralization pit. The operator visually watches the CBM's come out of a discharge pipe into the South neutralization pit. When the operator sees a color change, indicating that the CBM's have been evacuated from the vessel and polymer is now entering the South pit, the drain valve is then closed. The pH is checked manually with the use of litmus paper. When the solution in the South pit has reached a pH range of 7 to 9, the contents are then sent to the North pit for further treatment. Once the mixture is fully neutralized it is sent to waste water. On the January 19th, 2007, the operator had drained the CBM's out of the polymer surge drum and performed an unusually long draw. The draining of CBM's, which normally takes seconds, had taken three minutes. Depending on the position of the drain valve this could have introduced a large volume of polymer into the South pit. Polymer or acid soluble oils, (ASO), have a low pH and contain sulfur compounds. Later that day, a large volume of spent KOH was sent to the South pit, approximately 940 gallons. This would have been performed to further regulate pH. On the January 20th, 2007, the liquid level in the South pit was close to the top edge. At some point the drain valve on the South pit was turned in the open position. There is only one reason the drain on the South pit would have been opened; to lower the level in the pit because the contents were going to flow over the top of the pit. The drain on the South pit is normally closed, due to the fact that the contents have to be sent to the North pit for further treatment. On January 20, 2007, Employee #1 opened the drain on the South pit and the head pressure from the South pit released vapors. The vapors traveled up to Employee #1 who lost consciousness. No respiratory protection was worn by Employee #1, and he was wearing an H2S dosimeter. It is undetermined at this time if the dosimeter was working properly. When coworkers found Employee #1, they stated that the H2S monitor was alarming. The highest reading from the dosimeter was 95 ppm. The wind was blowing from the South but steam traps showed that the wind was also swirling near the pit. Employee #1 died from acute hydrogen sulfide intoxication.