Neurotoxin Gas

Neurotoxin gas is the weapon GLaDOS used against the people of Aperture Science. On the day she was activated, which fell on Take Your Daughter to Work Day, she turned on the researchers and killed nearly everyone in the facility with lethal doses of the gas; the surviving scientists installed a morality core to prevent further incidents. In Portal's final battle Chell knocks that core loose, and GLaDOS, revealing what it was, regains access to the neurotoxin emitters, which gives the fight its countdown timer; Wolpaw admitted the gas was a cheap way to simplify the battle's dialogue. In Portal 2 Chell and Wheatley sabotage Aperture's production of turrets and neurotoxin so GLaDOS cannot kill them before they attempt the core transfer.