Measured and perceived IEQ under different ventilation strategies in Swedish classrooms

Indoor environmental quality was assessed in Swedish primary school classrooms grouped into three categories based on the ventilation system: 1) natural or exhaust ventilation, 2) balanced mechanical ventilation systems with constant air volume (CAV), 3) balanced mechanical ventilation systems with variable air volume (VAV). Measurements of NO2, ozone, TVOC, formaldehyde, PM10, and PM2.5 and a questionnaire survey were conducted. The concentrations of pollutants were integrated into an Indoor Air Pollution Index allowing a rank comparison of classrooms. Children's perception scores were calculated based on the questionnaire responses. Naturally ventilated classrooms had higher level of air pollution. No significant differences in pollutant levels were observed between classrooms with CAV and VAV systems. The type of ventilation system affected the subjective assessment of indoor air quality; it was worst in naturally ventilated classrooms.