Evaluation of airborne transmission risk in university towns based on IEQ surveys

•Airborne transmission risk in university town during the pandemic is evaluated.•A 3-level evaluation method of transmission risk based on CO2 level is developed.•High CO2 concentration and transmission risk in all buildings except for canteens.•Economic and practical measures are recommended for improvements.•Demand controlled ventilation with a low CO2 setpoint is an appropriate system. This study aims to evaluate airborne transmission risk in university towns during the COVID-19 pandemic based on surveys of indoor environmental quality (IEQ). Both on-site measurements and questionnaire surveys were carried out in public buildings in university towns in Changsha, China. Air temperature, relative humidity, and CO2 concentration in one library, ten classrooms, eight canteens, seven restaurants, and sixteen malls were measured. 2220 valid questionnaires concerning occupants’ sensation on thermal environment, air movement, and indoor air quality were collected. A 3-level evaluation method of airborne transmission risk that is dependent on building type and indoor CO2 concentration was developed. Excessive CO2 concentration is found in library (1045 ppm), classrooms (1151 ppm), restaurants (1242 ppm), and malls (1057 ppm). The percentage time of “high risk” accounts for 18–100% in these buildings. The results reveal a serious problem: numerous public buildings in China and probably other resource limited countries are not basically prepared and equipped to cope with airborne transmission. This fact should be taken into account when developing guidelines and formulating mitigation measures. Real-time monitoring and displaying IEQ and thus the transmission risk level should be an important way to be widely implemented in public buildings. [Display omitted]