Research on airborne pathogen movement indoors has intensified since the COVID-19 pandemic. Virus-borne droplets are released via respiratory activity, may stay airborne for hours, and be transported around a room by ambient flow. This paper examines how the flow introduced by an air-sanitizing device interacts with a room geometry and HVAC, for which little information is available. It addresses the recirculating air patterns created, how these are affected by an HVAC system, and which HVAC configuration will potentially be more effective at pathogen reduction. The approach is computational fluid dynamics (CFD) and experiments of a test room to qualitatively validate the CFD, in addition to quantitative validation, then using CFD to evaluate three HVAC cases. The newly-patented device removes air near the floor via an inlet fan, passes it through a chamber with amplified UVC light for deactivation, and outputs clean air near the ceiling to produce recirculating zones. The experiments deliver a glycerin-water fog through the device and record movies for qualitative visualization. The CFD employs high-fidelity Ansys Fluent simulations with a Lagrangian aerosol model, and qualitatively agrees with 1- and 2-device experiments. With the HVAC supply near the device and return farther away, the CFD shows that less particles from talking and coughing stay airborne, and the device and HVAC inactivate/remove more particles than with the return and supply switched. This results from the device output flow being enhanced by the HVAC supply, leading to greater room-flow recirculation and more particle deposition on the floor.