With this type of system, the air treatment and refrigeration plants may be located some distance from the conditioned space in a central mechanical equipment room. Only the final cooling-heating medium (air) is brought into the conditioned space through ducts and distributed within the space through outlets (grilles, slot diffusers, ceiling diffusers, perforated ceiling panels, variable diffusers) or mixing terminal outlets (via mixing boxes).

The common names for some of the all-air types are: