At 2:30 p.m. on September 13, 2010, Employee #1, Employee #2, and Employee #3 were tasked with the dismantling of a scaffold level within a phosgene containment dome. During their dismantling work, at approximately 80 feet above the ground, alarms specific to phosgene gas were triggered. The process within this Dome was the manufacturing and use of phosgene to facilitate the production of PMDI (an isocyanate). The leak occurred when an employee of another contractor, working below the three scaffolding employees, removed a “slip blind” between a valve and a downstream section of pipe. The valve and subsequent piping were used to transport liquid phosgene. After the bolts connecting the valve and line were broken, the valve continued to leak phosgene, triggering the alarms. The phosgene dosimeter badges worn by Employee #1, Employee #2, and Employee #3, provided by the host facility, turned a color indicating exposure to between 50 to 100 ppm of phosgene. The host facility ERT transported these employees to the hospital where they stayed for at least eighteen hours for treatment.