Classroom airing behaviour significantly affects pupil well-being and concentration performance - results of a large-scale citizen science study in Danish schools

This study surveyed the indoor environment in Danish classrooms and explored its associations with pupil well-being and performance. It was a large-scale citizen science study using a simple intervention carried out over two days. On one of these days, the participating classes carefully aired out the classroom during the break before a lesson dedicated to measuring the classroom environment. They did this by keeping windows open and leaving the classroom during the break. On the other day, they were told to do as they usually do, i.e. they received no instruction to follow a particular airing behaviour. The order of the two airing behaviours was randomly balanced between classes. Measurements were reported by 709 classes in 234 schools and 640 classes completed a building checklist. In total, 21,326 well-being surveys and 20,701 concentration tests were completed by the pupils. Of these, a gross subsample of 13,094 records qualified for further analysis. With the instructed airing behaviour, the percentage of classes with a CO₂ concentration higher than 1000 ppm was reduced from 53% to 36% as compared with uninstructed behaviour. This finding corresponded with earlier related studies carried out in Danish classrooms in 2014 and 2009. Airing also improved the pupils' perception of the classroom environment, alleviated their building-related symptoms and increased their performance of a concentration test in which they made 6% fewer errors than with uninstructed behaviour. Based on responses from a large number of pupils, the findings confirm that inadequate classroom ventilation negatively affects pupil well-being and concentration and that classroom air quality continues to present a challenge in many Danish school buildings.