Environmental controls were often used to deploy certain chemicals ship-wide or station-wide. This was done for both benign purposes, such as the release of a retrovirus to cure a ship-wide epidemic, (TNG: "Genesis" ; VOY: "Macrocosm") or for more aggressive purposes such as the release of a general anesthetic. (ENT: "Chosen Realm"; TOS: "Space Seed" ; TNG: "The Hunted" , "Clues" ; VOY: "Message in a Bottle"; DS9: "Tacking Into the Wind")