Evaluation of Air Quality in a Primary School Classroom During Wintertime

The levels of gas and particulate pollutants were measured inside and outside of a primary school classroom located in a suburban area in the city of Patras, Greece, during wintertime to evaluate the indoor air quality, identify potential problems, and determine the effectiveness of ventilation. The Foundation for Research and Technology–Hellas (FORTH) mobile laboratory was deployed, and a switching valve system was used to obtain both indoor and outdoor measurements. The outdoor air was the main source of in-classroom pollutants, as the windows remained partially open. Ventilation of the classroom was achieved naturally through the windows, and it was continuous during school hours, maintaining the pollutant concentrations at low levels, with average fine particulate matter equal to 2.6 μg m⁻³ and total aromatic and oxygenated volatile organic compound (VOC) levels in the order of 10 ppb. The levels of all measured pollutants were lower than the World Health Organization (WHO) safety limits, and they are not expected to affect the health of the students. Good air quality was observed within the classroom, showing the effectiveness of natural ventilation in this setting. Cleaning activities were a source of VOCs outside school hours, resulting in increases in the levels of VOCs of a few parts per billion. However, these concentrations were gradually reduced, and they did not reduce the indoor air quality the next school day. A box model was used to estimate an effective air exchange rate of 3.5 h⁻¹ during school hours.