Systematically quantifying the dynamic characteristics of PM 2.5 in multiple indoor environments in a plateau city: Implication for internal contribution

People generally spend most of their time indoors, making a comprehensive evaluation of air pollution characteristics in various indoor microenvironments of great significance for accurate exposure estimation. In this study, field measurements were conducted in Kunming City, Southwest China, using real-time PM sensors to characterize indoor PM in ten different microenvironments including three restaurants, four public places, and three household settings. Results showed that the daily average PM concentrations in restaurants, public spaces, and households were 78.4 ± 24.3, 20.1 ± 6.6, and 18.0 ± 4.3 µg/m , respectively. The highest levels of indoor PM in restaurants were owing to strong internal emissions from cooking activities. Dynamic changes showed that indoor PM levels increased during business time in restaurants and public places, and cooking time in residential kitchens. Compared with public places, restaurants generally exhibit more rapid increases in indoor PM due to cooking activities, which can elevate indoor PM to high levels (5.1 times higher than the baseline) in a short time. Furthermore, indoor PM in restaurants were dominated by internal emissions, while outdoor penetration contributed mostly to indoor PM in public places and household settings. Results from this study revealed large variations in indoor PM in different microenvironments, and suggested site-specific measures for indoor PM pollution alleviation.