Emergency switch failed to close valve

USA: As investigations into Wednesday’s fatal ammonia leak in Boston begin, a local fire official has revealed that an emergency shut-off valve may not have worked.
The incident on Wednesday evening at the Stavis Seafoods plant in South Boston resulted in the death of a worker, now named as facilities manager and father of two Brian Caron of Peabody, Massachusetts.
Boston Fire Department spokesman Steve MacDonald told the Boston Globe that when five workers at the plant smelled ammonia, they pushed an emergency switch to shut off a valve, then rushed out the door. However, the leak from a ruptured 1½in metal pipe on the second floor of the cold storage warehouse didn’t stop and only four workers made it out alive.
“The valve should have shut off by hitting the switch,” said Steve MacDonald, who also revealed that the emergency response was slowed by the fact that the ammonia shut-off valve was in the middle of the building on the second floor.