Use of Carbon Dioxide (CO2) Monitors to Assess Ventilation Effectiveness in Schools

Abstract

The COVID-19 pandemic has highlighted the importance of good ventilation in mitigating the transmission of airborne virus particles. In many countries, CO₂ monitors have been mandated for use in indoor spaces to inform good ventilation practices. However, there is limited guidance on the use of CO₂ monitors to assess ventilation performance in large groups of buildings. In occupied classrooms, locating multiple monitors to collate reliable environmental data can be a difficult task because of the functions and usage of the space. This study used observations and physical measurements of CO₂ in three real-world naturally ventilated classrooms, in three primary schools to assess whether the use of a single CO₂ monitor, in one location could predict the room ventilation performance. The results indicate that for naturally ventilated classrooms, a single CO₂ monitor placed at head height (about 1.5 m) on a vertical wall, away from windows, doors, or air supply, and not directly under the breathing zone of occupants can be used to express the ventilation performance of classrooms. This study provides a systematic method for monitoring CO₂ to direct ventilation intervention programmes for large groups of school buildings.