Indoor air modelling and infection risk assessment in a naturally ventilated patient room

Sufficient ventilation in clinics is critical for diluting virus concentrations and lowering subsequent doses inhaled by the occupants. Several advanced simulation methods and tools for building physics and indoor air fluid dynamics are currently available in research and industry. However, in naturally ventilated buildings, indoor air distribution depends strongly on local and dynamically changing conditions, e.g., opening sizes and time, exhaust shaft location, and climatic and weather conditions. Therefore, considering the physical complexity of air and temperature distribution in natural ventilation rooms, new reliable and handy modelling techniques are required to predict infection risks of COVID-19 in typical naturally ventilated spaces.
This study includes field measurements and simulations of indoor air quality and building performance in a naturally ventilated hospital building. The indoor air model is built into the building energy simulation tool IDA-ICE to calculate air change rates in a naturally ventilated patient room. An initial data set was collected from the presurvey, architectural plans, and observations. The model was calibrated against indoor air measurements. Then, simulated air changes and room conditions were used for infection risk calculation. The virus-specific parameters of the infection risk model and human activity values are estimated separately using scientific literature studies. According to measurements and simulations, natural ventilation is insufficient to dilute airborne impurities in this case study. Additionally, the infection risk analysis indicated that the infection emission rate had a significant impact on the results of different ventilation strategies. The combination of controlled ventilation and air purification reflects a comprehensive and proactive approach to managing infection risks in patient rooms and healthcare settings. The simulation tool can help engineers and designers explore different ventilation strategies and infection control measures.