Abstract

During the COVID-19 pandemic, patient rooms in a South Korean hospital were converted into temporary negative-pressure isolation rooms (TNPIRs) using HEPA filtration units (PHFUs). We analyzed data from three multi-bed TNPIRs under four PHFU conditions, assessing airflow rates, room pressure differentials, HVAC terminals velocities, and sulfur hexafluoride (SF₆) tracer gas diffusion paths. Results showed that variability in PHFU performance produced uneven air change rates and pressure imbalances, while unintended airflow persisted through diffusers and grilles despite the central air-handling unit remaining inactive (HVAC). Additionally, tracer gas migrated via multiple routes including the plenum space above the T-bar suspended ceiling system, and some exhausted air re-entered the rooms. To address these issues, we propose real-time monitoring with automated controls and backup PHFUs; testing, adjusting, and balancing (T.A.B.); sealing HVAC terminals or installing backdraft dampers; and improving architectural airtightness. These proposed measures aim to manage airflow, strengthen airborne transmission control, and ensure environmental safety during public health emergencies.