Abstract: Employee #1 was in charge of monitoring the process of using steam to distill essential oils from plant material. The 8 ft deep steam distillation vessel has an inner diameter of 89 1/2 in. and a conical-type lid that fastens on top. The vessel is positioned so that the lid joint is approximately 2 1/2 in. above the working platform--waist level--so the operator can access it. Plant material is placed on top of a removable grate/screen, compacted, and secured before the lid is fastened by a series of 12 strongback devices. Steam is then applied at the bottom at a pressure range of between 95 and 125 psi. The steam travels up through the material, extracting the essential oil, and then through a 10 in. wide opening in the lid that tapers down to 2 1/2 in. before entering a cold water condenser tube, where the oil/water vapor is converted to a liquid. The liquid is captured and run through a separator, where the essential oil is separated from the water for collection. The process lasts for approximately 2 1/2 hours. At the time of the accident, the material had been processing for between 40 and 45 minutes when, for some reason, the vessel began to overpressurize, causing a critical upset condition and a rupture at the lid/cover joint. Employee #1 was standing directly next to the vessel when the lid violently separated from it, discharging the pressure and material outward. He was struck in the head, and died as a result of his injuries.