2020 Yes https://www.sciencedirect.com/science/article/pii/S0160412019338838 Vornanen-Winquist Europe Experimental Exposure Study Teachers Students Ventilation rates Temperature Humidity Carbon Dioxide (CO2) Volatile Organic Compounds (VOCs) Bacteria Fungi Respiratory symptoms Vision Headaches Indoor air quality School Trichoderma Microbes Online questionnaire Using air sampling as well as exhaust air filters and classroom settled dust to detect the presence of elevated concentrations of airborne cultivable microbes and pathogenic, toxigenic and mycoparasitic Trichoderma straine were the most indicative methods in distinguishing problematic schools from comparison schools. Other IAQ-related measurements did not detect clear differences between problematic schools and comparison schools, as the concentration levels were very low.