A system for circulating and conditioning air within a nuclear reactor habitability area is provided. The system may include an upper plenum formed between a lowered ceiling partition within the habitability area and a ceiling of the habitability area and a lower plenum formed between a raised floor partition within the habitability area and a floor of the habitability area. The system can additionally include at least one recirculation air handling unit located within the habitability area, the at least one recirculation air handling unit operable to generate a recirculation air flow within the habitability area by circulating air between the lower and upper plenums absent any air carrying ductwork routed through the ceiling, floor or walls of the habitability area.