The underpinning factors affecting the classroom air quality, thermal comfort and ventilation in 30 classrooms of primary schools in London

The health and academic performance of children are significantly impacted by air quality in classrooms. However, there is a lack of understanding of the relationship between classroom air pollutants and contextual factors such as physical characteristics of the classroom, ventilation and occupancy. We monitored concentrations of particulate matter (PM), CO2 and thermal comfort (relative humidity and temperature) across five schools in London. Results were compared between occupied and unoccupied hours to assess the impact of occupants and their activities, different floor coverings and the locations of the classrooms. In-classroom CO2 concentrations varied between 500 and 1500 ppm during occupancy; average CO2 (955 +/- 365 ppm) during occupancy was similar to 150% higher than non-occupancy. Average PM10 (23 +/- 15 mu gm(-3)), PM2.5 (10 +/- 4 mu gm(-3)) and PM1 (6 +/- 3 mu g m(-3)) during the occupancy were 230, 125 and 120% higher than non-occupancy. Average RH (29 +/- 6%) was below the 40-60% comfort range in all classrooms. Average temperature (24 +/- 2 degrees C) was >23 degrees C in 60% of classrooms. Reduction in PM10 concentration (50%) by dual ventilation (mechanical + natural) was higher than for PM2.5 (40%) and PM1 (33%) compared with natural ventilation (door + window). PM10 was higher in classrooms with wooden (33 +/- 19 mu g m(-3)) and vinyl (25 +/- 20 mu gm(-3)) floors compared with carpet (17 +/- 12 mu gm(-3)). Air change rate (ACH) and CO2 did not vary appreciably between the different floor levels and types. PM2.5/PM10 was influenced by different occupancy periods; highest value (similar to 0.87) was during non occupancy compared with occupancy (similar to 0.56). Classrooms located on the ground floor had PM2.5/PM10 > 0.5, indicating an outdoor PM2.5 ingress compared with those located on the first and third floors (<0.5). The large volume (>300 m(3)) classroom showed similar to 33% lower ACH compared with small-volume (100-200 m(3)). These findings provide guidance for taking appropriate measures to improve classroom air quality.

Automated summary

This study monitored the air quality in classrooms in five schools in London, finding that classroom air pollution, including particulate matter and CO2 concentrations, is affected by various factors such as classroom characteristics and ventilation. The results show that CO2 concentrations during occupancy were 150% higher than non-occupancy, and PM concentrations during occupancy were significantly higher compared to non-occupancy. Overall, the air quality in classrooms was found to be poor.