Co-creation of an airflow and COVID-19 transmission risk model for humanitarian shelter design

Ventilation rates in overcrowded humanitarian shelters are often insufficient to prevent condensation, respiratory illness, and the transmission of airborne diseases. Enhancing ventilation is challenging due to security needs, protection from dust and insects, and a lack of design expertise among humanitarian teams without engineering backgrounds. This study presents the development, validation, and testing of a novel natural-ventilation and infection-risk assessment methodology co-designed with 42 practitioners from NGOs, humanitarian organisations, and academia through a six-phase participatory process. The new methodology requires approximately 20 inputs to characterise shelter conditions across more than 3100 global locations and performs natural-ventilation, indoor CO₂, and COVID-19 transmission-risk calculations without the need for prior airflow-modelling knowledge. Model performance was evaluated against established network models (EnergyPlus Airflow Network and CONTAM) using representative shelters in Ethiopia, Djibouti, and Nepal, demonstrating good agreement. Usability testing with 12 aid workers showed that first-time users could complete a full shelter assessment in about 30 min, with subsequent iterations requiring around 15 min. The method provides a rapid, accessible method for estimating ventilation adequacy and airborne-diseases risk in resource-constrained settings and has been adopted by several humanitarian agencies to support emergency shelter design and ventilation decision-making.