France conducted a training exercise in one of Paris' busiest metro stations Wednesday night to test their capacity to cope with a terrorist chemical weapons attack. The exercise, which took place at midnight, involved 500 police, firefighters and rail staff, according to the Agence France Presse. During the exercise, an imaginary release of toxic gas inside the Invalides station triggered an emergency program codenamed Piratox, and rescue workers with special equipment rushed to the scene to treat victims and contain the damage. The aim of France's first-ever exercise was to put into practice procedures devised since the September 11, 2001 terrorist attacks in the U.S., testing the effectiveness of protection suits, medical apparatus and communication systems.