Nearly 20 years later, in 2004, an internal DuPont safety study recommended adding an enclosure for the phosgene operation at Belle. The study said such an enclosure would help prevent "multiple fatalities" from the release of phosgene from the 2,000-pound cylinders being used in the shed.
Initially, the due date for construction of the enclosure was December 2005. That was extended until December 2006.
"Work to define the scope of this item is progressing, but not yet complete," a DuPont memo written in 2006 said. "We are evaluating potential lower cost alternatives to total shed enclosure."
The due date was extended three more times, and the enclosure wasn't completed at the time of the January 2010 leak, the CSB reported.
CSB investigators said a completely enclosed phosgene unit would not only protect nearby communities from a toxic leak, but also make things safer for workers inside the plant. An enclosed facility could have allowed workers to change phosgene tanks without entering the area, by using protective gloves built into the unit. Also, the enclosure would have been equipped with a scrubber to contain any leaks that did occur, the CSB investigators said.
"The right way to do it would be to have the phosgene completely enclosed," said CSB member John Bresland, a longtime chemical plant manager and former DuPont lab technician.
In addition, CSB investigators criticized DuPont's policy of not requiring complete "personal protective equipment," or PPE -- such as protective suits or breathing devices -- for all work around the phosgene cylinders.
Johnnie Banks, the CSB's team leader for the Belle investigation, said DuPont actually had been storing protective suits inside the phosgene shed, so that workers would have to enter that area before they could don the suits.
CSB officials noted that a DuPont plant in Mobile, Ala., uses the same one-ton phosgene cylinders as had been used at Belle.
"The phosgene cylinders and weigh scales at the Mobile plant are housed in an enclosed room," the CSB report said. "The cylinder room vents to an emergency scrubber that pulls a slight negative pressure on the room and scrubs air before venting to the atmosphere.
"The scrubber is designed to capture vapors from a release of an entire cylinder," the CSB reported. "Operators at the Mobile plant enter the phosgene cylinder area under the same PPE requirements as Belle for isolating and changing cylinders (hard hat, steel-toed shoes, safety glasses, and phosgene dosimeters). However, at Mobile, to capture and scrub phosgene vapors in the event of a release, the operator turns on the emergency scrubber and pump before entering the enclosure."
CSB investigators explained, "Like Belle, Mobile has phosgene analyzers located in and around the unit to continuously monitor concentrations. At Mobile, alarms in the cylinder enclosure activate local audible alarms inside the enclosure and a flashing light outside to alert employees. If no operators are present in the enclosure when the alarm activates, the emergency vent scrubber automatically starts.
"The Belle plant analyzer in the phosgene shed had no audible alarm to alert personnel in the area; instead, Belle plant procedures require the board operator to notify personnel of the release and only operators at the phosgene shed can activate the switch for the warning light," the CSB report said.
"The emergency scrub system and automated alarms at Mobile are examples of higher level controls that protect workers from hazards," the report said. "Mobile has automated alarms where Belle relies on operator action to initiate alarms to warn personnel of a suspected or actual release.
"Mobile implemented the scrubber system, an example of an engineering control, to manage the concentrations of phosgene in the cylinder enclosure in the event of a release," the report said. "The Belle plant phosgene shed design allows only for natural ventilation to carry unwashed phosgene gases that can potentially harm personnel in or around the shed and possibly enter the community."
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.