Abstract: At approximately 9:00 a.m. on October 22, 2007, two employees parked a vacuum truck along the roadside near the Number 10 Reformer in a Refinery. The purpose was to vacuum liquids from the Y-3 Acid Sump and Skid. One employee began collecting liquid from the Y-3 acid sump through a hose into a vacuum truck parked approximately 40 ft away from the Y-3 sump. Employee #1 was standing at the rear of the vacuum truck operating the control valves. Several minutes into the vacuum operation, Employee #1 yelled to his coworker that he smelled a very strong odor. The coworker advised Employee #1 to move away from the vacuum truck moving beyond the other side of the vehicle. Employee #1 stepped out from behind the vacuum truck along the passenger side of the vacuum truck. A "gooseneck" vent pointing in a downward angle at the front portion of passenger side of the truck was venting copious amount of concentrated vapors consisting of Hydrogen Sulfide and possibly Methyl Mercaptan. Employee #1 inhaled the vapors and staggered to the other side of the plant road where he attempted to sit down but fell over according to witnesses. The coworker ran over to the vacuum truck to shut off the pump and proceeded around the front of the vehicle. At this time, Employee #1 had walked back to the vacuum truck and placed himself in the path of the vent again. Employee #1 collapsed. Two refinery employees, outside operators, that witnessed Employee #1 stagger across the street had retreated to a nearby control room to don fresh air packs. These outside operators removed Employee #1 from the location along side the passenger side of the vacuum truck. The outside operators attempted to revive Employee #1 who died due to the exposure.