ATMOS

ATMOS (Atmospheric Omission System) devices were used in the plans of the Sontarans to invade Earth in 2009. ATMOS devices were fitted to automobiles to reduce carbon dioxide emmissions to zero. They could be threaded in every kind of car, and included a computer system at the dashboard.

The ATMOS devices were sold to Humans by the company owned by Luke Rattigan, supposed to be his own invention even though it was decades ahead of Earth technology of the time. When they first came onto the market UNIT suspected they might be alien, but their investigations turned up nothing. However, after a series of simultaneous accidents involving ATMOS-fitted cars, they called in the Doctor and it was soon discovered that their ulterior usage was that they were to be used as weapons by the Sontarans, as it gave them control over the cars and released poisonous fumes.

There were 17 factories worldwide, though the ATMOS Factory in London served as a central depot. By 2009 it was fitted in 400 million of the 800 million cars on Earth, including all vehicles utilised by the British government. (DW: The Sontaran Stratagem / The Poison Sky)

Behind The Scenes
ATMOS is a major plot element of The Sontaran Stratagem / The Poison Sky. However, the word "ATMOS" first appeared on a taxi in Partners in Crime.

Naming
ATMOS meant Atmospheric Omission System, so when the Doctor called it ATMOS system, he was officially incorrect, as then it would be Atmospheric Omission System system, which is unnecessary.