Air filtration and handling for nuclear reactor habitability area

A system for circulating and conditioning air within a nuclear plant, said system comprising:

• a habitability area with walls, a ceiling and a floor;
• an upper plenum formed between a ceiling partition within the habitability area and the ceiling of the habitability area, the ceiling partition including a plurality of air vents;
• a lower plenum formed between a raised floor partition within the habitability area and the floor of the habitability area, the floor partition including a plurality of air registers;
• a pair of redundant recirculation air handling units located within the habitability area, each recirculation air handling unit including an air inlet fluidly connected to the upper plenum, an air outlet fluidly connected to the lower plenum and a fan operable to generate a forced air flow through the respective recirculation air handling unit by drawing air in from the upper plenum through the respective air inlet and forcing air out into the lower plenum through the respective air outlet such that a recirculation air flow is created throughout the habitability area by air flowing out of the lower plenum through the floor partition registers and into the upper plenum through ceiling partition vents;
• and
• a smoke purge subsystem including,
• a smoke purge fan located exterior to the habitability area and directly connected to the upper plenum via smoke purge outlet ductwork, and
• exterior air inlet ductwork connecting an exterior air access to the lower plenum via the exterior air inlet ductwork,
• the smoke purge fan being a dedicated fan for the upper plenum of the habitability area and being operable to draw exterior air into the habitability area through the exterior air inlet ductwork and purge air from within the habitability area to an environment exterior of the habitability area through the smoke purge outlet ductwork, the lower plenum being a supply plenum for the recirculation air flow and the upper plenum being a return plenum for the recirculation air flow,
• wherein the smoke purge fan is further operable to draw the exterior air into the habitability area through the exterior air inlet ductwork and purge air from within the habitability area to the environment exterior of the habitability area through the smoke purge outlet ductwork even during periods when the pair of redundant recirculation air handling units is not in operation.