Personalised ventilation to prevent airborne disease transmission in portable site sheds

Portable site sheds, used as refectories, changing rooms, meeting rooms, or offices, are workplaces with a high occupancy rate. However, the sheds are generally not mechanically ventilated, with closed doors and windows in case of bad weather. These conditions lead to a low air change rate and generate a high risk of airborne disease transmission among the occupants. Moreover, this collective protection equipment cannot be supplemented with personal protection in refectories, where wearing masks is not practical. In this paper, the natural airflow rate due to infiltration is first estimated based on the decay of carbon dioxide concentration in a standard portable site shed. Then, a personalized mechanical ventilation system is designed using computational fluid dynamics (CFD) simulations of both the airflow and the carbon dioxide exhaled by the occupants. To avoid direct droplet transmission of diseases, the influence of transparent separation walls is also assessed. The designed ventilation system is implemented in a portable site shed, then verified based on measurements of fresh air supply to each occupant, in relation to thermal comfort and acoustic comfort.