Investigation of indoor total volatile organic compound concentrations in densely occupied university buildings under natural ventilation: Temporal variation, correlation and source contribution

Abstract

Human activities have been proven to be one of the most important sources of indoor volatile organic compound (VOC) emissions, especially in densely occupied environments. However, characterization of temporal variation and its impact analysis of indoor total volatile organic compounds (TVOC) have not been presented adequately. In this study, indoor concentrations and temporal variation of TVOC concentrations were investigated using a continuous monitoring instrument in 20 densely occupied education buildings randomly selected at one university in Nanjing, China, including nine lecture halls and 11 classrooms. Indoor and outdoor CO2 concentration, temperature and relative humidity were monitored to analyse the correlation and contribution rates of TVOC from indoor and outdoor sources. Results show that the variation in the indoor TVOC concentration was similar to the indoor CO2 concentration in densely occupied education buildings with the exception of sudden indoor sources, such as food service. Further analysis indicates that a strong positive correlation was observed between the number of occupants and TVOC concentrations. The average contribution rate could reach 69.2% from indoor sources and 30.8% from outdoors. This study provided a better understanding of the status quo and could help in developing control strategies of indoor air quality in densely occupied education buildings.