Atmospheric converter

An Atmospheric Converter was used by the Doctor in order to clear the Earth's atmosphere of the ATMOS gas. It set fire to the atmosphere and dispersed the gas. The Doctor then 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 changes atmospheres into Oxygen. (DW: The Poison Sky)