Code 6

Code 6 is the name of the evacuation procedure for CTU.

During Day 5, Jack Bauer realized that Ostroff (whom he had just killed) planned to release a canister of nerve gas in CTU's ventilation system. Bill Buchanan immediately called for a Code 6 evacuation.

Due to the confusion caused by having called a lock-down right before, the facility was not properly evacuated, and about 40% of CTU's staff was killed due to the nerve gas.