In response to the WHO and UN’s call to ensure children’s right to breathe “clean” air and the challenges posed by the COVID-19 pandemic on maintaining healthy indoor air quality (IAQ), this PhD research explores ventilation and air cleaning strategies to control the spread of infectious respiratory particles (IRPs) in school classrooms.
The study follows four key steps: (1) a literature review bridging school ventilation regimes, IRP transmission, and advanced ventilation systems; (2) a field study to evaluate real-world ventilation and thermal conditions during the pandemic; (3) an experimental investigation of performance of mobile air cleaners (MACs) followed by an in-situ validation; and (4) a combined experimental and computational study to assess personalized air cleaners (PACs) as localized exhaust for IRP removal.
Findings reveal that most classrooms rely on natural ventilation, often failing to meet IAQ standards, especially when fully occupied. With windows and doors open, ventilation rates remained inconsistent, and thermal conditions were unsatisfactory. Hence, more controllable ventilation and air cleaning approaches are needed. MACs, when appropriately selected and positioned, offer effective protection against long-range IRP transmission at room scale, while PACs are effective at mitigating localized, short-range IRP exposure, improving IAQ at an individual level.
This research offers a comprehensive set of solutions for IRP control in classrooms, with actionable insights for a variety of stakeholders. It advocates for a shift from comfort-based to health-centered paradigms. Future research should explore hybrid systems, optimize designs, and validate interventions through real-world infection risk assessments to create healthier, more resilient classrooms.@en

The airborne transmission of SARS-CoV-2 in educational buildings has raised concerns during the current COVID-19 pandemic. In this study, a portable fog generator system was designed and assembled to visualise the airflow pattern of exhaled droplets in a classroom. The system consists of five components: medium, fog generator, buffer, pump, and manikin head. The medium was made of a combination of glycol and demineralised water, which produced a fog composed of droplets mimicking to some extent human breath. The fog was produced with the fog generator and passed through a pipe into the buffer for build-up. After accumulation, the fog is pumped through another pipe and is exhaled out of the mouth of the manikin. The experiments were conducted in a simulated classroom. The lights of the room were dimmed and six lasers were used to make the fog more visible. Four different ventilation regimes were examined: no ventilation, natural ventilation (open windows and door), mixing ventilation (600 m3/h), and a combination of natural + mixing ventilation. The experiments were recorded with a camera and analysed to determine the horizontal distance of the path taken by the fog and to measure the time it remained visible after exhalation from the mouth. During the experiments, it could be observed with the naked eye that the glycol droplets travel much further and linger in the air for longer than what is captured in the recordings. Furthermore, not all the droplets were visible with the camera, especially the smaller ones of a few micrometres in diameter. The recordings showed that at the natural ventilation regime the droplets travelled the furthest distance (1.8 metres). This wind coming through the door pushed the drops further into the room. The combination of natural + mixing ventilation regime had the highest indoor air velocity, causing the droplets to reach the shortest distance (0.5 metres). In conclusion, the type of ventilation, classroom layout, and exhalation location play an important role in determining the airflow pattern, as they affect how long and how far the glycol droplets travel. Applying any type of ventilation is critical in transmission control and reduces the possibility of aerosol accumulation in the classroom as smaller droplets can linger in the air for many hours until they settle on a surface.

A design for a garment factory in Bandung (Indonesia). The focus is on the indoor environment: lighting, indoor air quality, thermal comfort and acoustics.