The atmosphere factory is a large and highly-guarded facility maintained by Helium. It is responsible for providing the air that keeps all life on Barsoom alive. The factory utilizes the ninth ray of sunlight, separating it out from the other eight rays using instruments on the factory's roof. The ray is converted into energy and stored in one of several enormous reservoirs, at which point an electrical current is introduced that presumably converts the energy into a gas.
Everyone on Barsoom recognizes the importance of the factory (though some peoples believe the factory a ruse to keep others subjugated), and its security is severe: the factory's walls are one-hundred and fifty feet thick, and its roof is covered with glass five feet thick. Even if there was someone demented enough to try and attack the factory, they would almost certainly fail. At any given time, there are only two people who know the secret to opening the doors to the factory, which are operated via a combination of thought waves. These men live an almost monk-like existence; for 344 days (half of a Martian year), one man will be confined to the factory, while the other is permitted to travel. They wear no clothing except for a gold collar from which hangs a diadem the size of a dinner plate. The diadem is set with huge diamonds, and in the center is an extremely rare stone that scintillates all nine rays of light. This ornament serves as a signal to all Martians that the bearer is responsible for maintaining their atmosphere, and thus must be allowed to travel unmolested.
The yellow Martians also operate their own similar installation capable of sustaining the northern pole if the primary atmosphere factory were to fail.