Code Black was a distress call used by Torchwood, calling for available agents to set out "guns blazing". (AUDIO: Blind Summit)
Code Black was called when the Law Machines fell under WOTAN's control and attacked London, leaving Torchwood Tower undefended and vulnerable to infiltration by Julian Delaware. (AUDIO: The Law Machines)
Toshiko Sato tried to alert Owen Harper to a Code Black at the Cardiff Bay Millennium Hall, but she was unable to contact him. (AUDIO: Dinner and a Show)