Abstract: Cylinder Number 7938 was removed from the Dewar at the side dock and placed in front of the vacuum pump and to the side of the scale. The best estimate is that the cylinder was 30-inches from the north wall and 53-inches from the west wall. Since the weigh scale was occupied by a collector, the operator attended to other activities. At some point he left the fill room to check on the arsine scrubber. While he was doing this the cylinder ruptured. The rapid release of the contents propelled the cylinder in a northwest direction and lifted it off the ground. The cylinder bottom impacted the west wall at an angle of approximately 17-inches above the floor, shattering the concrete block.. The block fragments then impacted the outer surface and blew the fragments into the hallway. On initial impact the cylinder cantilevered upward and impacted the manifold. This bent the manifold and sheared a piping connection. The cylinder then fell onto the collector on the scale. Fourteen employees were exposed to the poison gas from the ruptured cylinder and were hospitalized for treatment.