On July 15, 2009, a cargo transfer hose ruptured shortly after transfer of anhydrous ammonia began from a Werner Transportation cargo tank truck to a storage tank at the Tanner Industries facility in Swansea, S.C.
A white cloud of anhydrous ammonia, which is toxic when inhaled, moved from the parking lot across U.S. Highway 321 to a largely wooded area. A motorist drove into the ammonia cloud, apparently tried to get away from the cloud, then got out of her car and died of ammonia poisoning.
Fourteen people experienced minor respiratory problems or dizziness; seven were taken to the hospital and treated and released the same day.
NTSB investigators determined that the probable cause of the accident was Werner's use of a cargo hose assembly that was designed for liquefied petroleum gas (LPG) transfer only and was not chemically compatible with anhydrous ammonia.
Laboratory testing showed the rupture in the hose started from the inside of the hose, and some of the reinforcing braid fibers were degraded to the point where they were brittle and would crumble when gently probed.
Investigators discovered that the hose was not assigned to the trailer in the incident. It appears that somehow the anhydrous-ammonia hose originally on the trailer was exchanged with the LPG hose from another trailer while both trailers were stored on the same secure lot in Tampa, Fla., for several hours on May 17.
As a result of the investigation, NTSB issued a joint recommendation to the DOT's Federal Motor Carrier Safety Administration and Pipeline and Hazardous Materials Safety Administration to "jointly issue a safety advisory bulletin to inform cargo tank motor vehicle owners and operators, registered inspectors of these vehicles, and transfer facility operators about the circumstances of this accident and actions needed to prevent the occurrence of a similar accident."
You can read the entire recommendation letter in this PDF file.