The Life Support Systems are located in another of the Power Rooms. These systems include the Dimensional Stabilizers, Atmosphere Monitoring Subsystems, and the Auto-Gravity System. The Life Support Systems can support several thousands of humanoids. Minor life support needs, like interior lighting, are usually powered by the auxiliary power source.

Aside from the glowing roundels there are no obvious light sources in a TARDIS - nevertheless the interior will be quite well lit. The interior lights can be controlled from a switch on the console and can be raised to painful brightness. A TARDIS has an optional diurnal (day/night) cycle. Interior lighting, are usually powered by the auxiliary power source.

Normally the interior of a TARDIS is quite sterile. Given that there is only one case of the TARDIS crew spreading an organic virus from one time zone to another the TARDIS must have some sort of anti-viral software.