What’s Really in the Air Our Students Breathe?
Children spend a large proportion of their day in classrooms, making indoor air quality an important factor for both health and learning. But how does air quality vary between schools, and what can we learn from monitoring it over time?
Researchers from the CHILI team, Alice Handy, Sam Wood and Henry Burridge, set out to answer these questions using data collected through the Schools’ Air quality Monitoring for Health and Education (SAMHE) project.
Understanding Air Quality in Schools
The study examined data from 143 schools across the UK over two academic years, from 2023 to 2025, focusing on two key indicators of indoor air quality:
Carbon Dioxide (CO₂)
Carbon dioxide levels are commonly used as an indicator of ventilation. When CO₂ concentrations are high, it can suggest that a classroom is not receiving sufficient fresh air, which may affect pupils’ concentration, comfort and learning.
Particulate Matter (PM)
Particulate matter consists of tiny particles suspended in the air. These particles can come from both indoor and outdoor sources and may have implications for respiratory health when present at elevated levels.
What Did the Study Find?
Drawing on an impressive 190,031 school-days of monitoring data, the researchers found considerable variation in air quality across schools.
Key findings included:
- Both CO₂ and particulate matter levels varied substantially between schools.
- Particulate matter showed greater variation over time than between schools, reflecting the strong influence of outdoor air pollution and environmental conditions on what enters classrooms.
- CO₂ levels differed more between schools than over time, suggesting that school-specific factors play an important role.
These school-level factors may include:
- Classroom occupancy
- Pupils’ age groups
- Activity levels within classrooms
- Ventilation practices and building characteristics
Why Does This Matter?
Understanding how and why air quality varies in schools is essential for creating healthier learning environments. The findings highlight that while particulate matter is strongly influenced by changing outdoor conditions, ventilation-related factors can have a significant and lasting impact on indoor CO₂ levels.
By identifying the factors associated with poorer air quality, schools can make more informed decisions about ventilation and classroom management, helping to support both student wellbeing and educational outcomes.
A Collaborative Effort
This research was made possible thanks to the participation of schools across the UK that contribute data through the SAMHE project. Their ongoing involvement has created one of the largest datasets of its kind, enabling researchers to better understand indoor air quality in educational settings.
Read the Full Study
The findings have been published in the Journal of Indoor Environments.
Paper: What drives variation in indoor air quality among schools? Evidence from 190,031 school-days of monitoring data from the SAMHE project
🔗 https://dx.doi.org/10.1016/j.indenv.2025.100146
The study provides important evidence to support future efforts to improve air quality in schools and create healthier spaces for children to learn and thrive.
