In preparation of their 2009 invasion attempt of Earth the Sontarans manipulated humans to utilise ATMOS devices, seemingly a device to neutralise carbon dioxide emissions. However the true purpose of the ATMOS devices was to release Sezerfine gas into the atmosphere and thus turn the Earth into a clone world. The gas was eliminated from the Earth's atmosphere by the Tenth Doctor with Luke Rattigan's atmospheric converter. (TV: The Sontaran Stratagem / The Poison Sky, The Last Sontaran)