Preliminary assessment of CO2 concentrations and effects of natural ventilation during lectures in university classrooms of southern Italy

Italian university students spend a significant part of their daytime inside classrooms without controlled mechanical ventilation. Poor Indoor Air Quality (IAQ) can lead to both long-term and short-term health issues. Carbon dioxide (CO2) concentrations are usually used as a key indicator of IAQ in buildings and numerous scientific studies reported that prolonged exposure to relevant CO2 levels can cause headaches, drowsiness and concentration difficulties (which are crucial in learning environments). In this study CO2 concentrations inside three different classrooms of the Department of Architecture and Industrial Design of the University of Campania Luigi Vanvitelli (Aversa, southern Italy) have been measured with a time-step of 1 minute during lectures (lasting between 2 and 5 hours) carried out during spring and winter. The analyses have been carried out in classrooms without mechanical ventilation differing in terms of floor area, volume, number and area of openings, number of occupants per unit area (between 0.19 and 0.29 persons/m2) and per unit volume (between 0.03 and 0.06 persons/m3). The effects of natural ventilation via manual opening of windows and doors on CO2 concentration-time data have been also evaluated. The measurements showed that the presence of occupants increases CO2 concentrations with a rate ranging between 230 and 476 ppm after 30 minutes, achieving absolute values larger than 800 ppm after about 16÷38 minutes. The experimental data also showed that manual airing via opening doors and windows for a period of about 13÷26 minutes can be an effective strategy to mitigate CO2 concentrations down to outdoor values.