Atmospheric converter

An Atmospheric Converter was used by the Tenth Doctor to clear the Earth's atmosphere of the ATMOS gas. It set fire to the atmosphere and dispersed the gas. The Doctor planned to use it to ignite the Sontaran flagship and kill the Sontarans onboard. Luke Rattigan took his place and blew up the Sontarans and their flagship along with himself and the atmospheric converter. The device functioned by emitting a blast that changed some of the athomosphere's compounds into oxygen. (DW: The Poison Sky)