 Immediately after activation, the facility was flooded with deadly neurotoxin by the AI.Events of the first "Half-Life" game occur shortly after that, presumably leaving the facility forgotten by the outside world due to apocalyptic happenings.Wolpaw, in describing the ending of "Portal 2", affirmed that the Combine invasion, chronologically taking place after "Half-Life" and before "Half-Life 2", had occurred before "Portal 2"s events.