This system uses the Relative Dimensional Stabilizers to control the type and amount of atmosphere pumped into a TARDIS. The Subsystem has an automatic-cleaning device so used air is recycled, purified, and reclaimed by the Automatic Oxygen Supply System.

It automatically adjusts the internal temperature and humidity for the comfort of the crew. Despite this, humans often find the internal atmosphere somewhat drier than what they are used to. Trakenites, on the other hand find it uncomfortably warm and humid. If a TARDIS lands on a habitable planet it will draw air from the outside and filter it. If the interior hum is ever deactivated, then the life support system can be faintly heard. It sounds like very slow breathing. An alarm will sound if the life-support systems are about to fail.

It should be noted that the TARDIS 's Protyon Unit is vulnerable to high temperatures (over 40 degrees Celsius). There is an Emergency Unit with enough air for several hours. When the internal environment's temperature rises beyond a TARDIS's engineering tolerances then the automatic controls will be disabled. Venting the Thermo-Buffer can be used to cool the interior of a TARDIS when the environment is unstable. If exposed to freezing conditions for too long (say if the main doors are left open) the thermo-couplings might become chilled. This can result in a rocky dematerialization. For this reason it is important to keep the main doors closed if the exterior environment is sub zero.