On November 22, 1997, a frost ring that signified product leakage was discovered on the bottom center of a tank car that was being unloaded at the Georgia Gulf Corporation chemical plant in Pasadena, Texas. The tank car contained 29,054 gallons of a propylene/propane mixture, a liquefied flammable gas. The tank car had been purged with cryogenic nitrogen on October 17, about a month before the accident. No injuries or fatalities were reported as a result of the failure of the tank car. Georgia Gulf estimated that approximately 52 gallons of the cargo were released. The safety issues discussed in this report are the need to safeguard tank cars adequately when they are being purged with nitrogen and the use of engineering analyses of the properties of tank car steels in the development o industry-recommended procedures for the purging of tank cars with nitrogen. As a result of its investigation, the National Transportation Safety Board issued recommendations to the Compressed Gas Association, Inc., the Federal Railroad Administration, and the Association of American Railroads.