Carbon Dioxide Levels and Summertime Ventilation Rates in UK Schools

Measurements of metabolic carbon dioxide concentration made in four classrooms in two schools are reported for both occupied and unoccupied periods. Measurements were taken for approximately one week in each classroom during the unheated season and the time-varying ventilation rates estimated. The results of the experiments show CO2 concentrations that are far beyond the guideline value of 1000 ppm (the maximum concentration during the occupied period was 3756 ppm). Calculated air supply rates vary from unacceptably low levels, to rates that are in line with guidance. The occurrence of periods with acceptable supply rates, and the rates found during purge ventilation, show that the surveyed classrooms have the potential to provide adequate fresh air. Inaccessible windows and ventilation openings, combined with lack of guidance on when and how to apply ventilation seems to be the primary reason for poor ventilation outside the heating season.