Infectious cough droplet dynamics in a makeshift hospital isolation ward

The COVID-19 pandemic highlighted the need for rapidly deployable healthcare facilities, leading to increased use of modular construction methods. Nonetheless, knowledge about airflow patterns and the spread of bioaerosols in these wards remains insufficient, potentially heightening the risk of cross-infection among healthcare workers and patients. This paper presents a ventilation design for a modular negative-pressure ward aimed at reducing the spread of infectious particles. We investigate the effects of various ventilation designs, patient postures (sitting and supine), and air changes per hour (ACH) on the spread of infectious cough droplets in an airborne infection isolation room using large eddy simulation and the Eulerian-Lagrangian model. Findings show that ceiling exhaust grilles (design 2) resulted in the lowest radial dispersion (3.64 m) at 12 ACH, while sidewall exhausts (baseline) performed best at higher ACH levels. Seated patients had quicker droplet evaporation compared to those in a supine position. The best setups for reducing droplet survival included exhaust grilles at the bed's bottom and ceiling, maintaining a minimum of 12 ACH. Cases 5 and 13, with grilles over the patient's head and at the bed's bottom, showed the lowest concentrations of DPM, under 0.008 km⁻³ near the source and less than 0.001 km⁻³ mid-room. Sitting posture consistently led to lower DPM concentrations. This research emphasizes the critical role of exhaust placement in reducing droplet re-circulation and transmission risks, ultimately contributing to improved ventilation strategies and infection control in AII rooms.