Abstract: The invention is a disinfecting HVAC system that combines thermal displacement ventilation technology with UV-C light technology to isolate, concentrate, and/or kill harmful microorganisms (such as SARS-Cov-2) present in enclosed spaces. The system includes a single manifold collection pipe placed adjacent to the ceiling (e.g., about 12-14 feet above the floor). The collection pipe has a high collection efficiency when connected to an HVAC air handler and booster fan tandem. In the air handler, the warm air is cooled and treated with a sufficient dose of UV-C light to inactivate any microorganisms within a short amount of time. The UV-C treated air is then returned to the enclosed space through a plurality of low velocity diffusers.