Giulio Vita, Thomas Avery-Hickmott, Patricia Pino, Rob Rowsell, Darren Woolf
Languages: English | Pages: 10 pp
Bibliographic info:
42nd AIVC - 10th TightVent - 8th venticool Conference - Rotterdam, Netherlands - 5-6 October 2022

The COVID-19 pandemic has prompted huge efforts to further the scientific knowledge of indoor ventilation and its relationship to airborne infection risk. Exhaled infectious aerosols are spread and inhaled as a result of room airflow characteristics. Many calculation methods and assertions on relative airborne infection risk assume ‘well-mixed’ flow conditions. However, ventilation in buildings is complex and often not relatable to well-mixed conditions.  Ventilation guidance is typically based on the provision of generic minimum ventilation flow rates for a given space volume, floor area or occupancy level, irrespective of the effectiveness in the delivery of the supply air. Furthermore, the air movement might be influenced by the specific room characteristics and conditions (for example the opening of windows), which would potentially generate draughts (an example of a secondary consideration) and non-uniform flows. As a result, fresh air dilution could be highly variable depending upon a susceptible person’s position in a room and, as a result, associated airborne infection risk. 
A computational fluid dynamics (CFD) framework is presented to assess relative infection risk in a real building.  The coupled influence of wind on the internal airflow characteristics resulting from open windows is evaluated to test the framework’s capabilities. Using the 
‘transfer efficiency’ approach to evaluate relative infection risk , the results clearly demonstrate the importance of understanding detailed indoor airflow characteristics and associated dilution patterns in order to provide detailed ventilation design guidance, e.g. occupancy, vents and furniture layouts, to reduce relative airborne infection risk.