Effects of cooking and window opening behaviors on indoor ultrafine particle concentrations in urban residences: A field study in Yangtze River Delta region of China

Characterization of indoor ultrafine particles (UFPs, diameter <100 nm) in residences has been of great interest. However, insufficient information was presented with respect to the characteristics of typical occupants' activities and indoor UFP source emissions under actual conditions. In this study, a field investigation including questionnaire survey (N = 395) and field measurement (N = 38) was conducted in urban residences in two cities of the Yangtze River Delta region of China. The results indicate that outdoor air temperature was identified to be positively correlated (r = 0.106, p < 0.05) and the most influential factor on window-opening behaviors in living room and bedroom. Instead, most of residences prefer to keeping kitchen window opening and kitchen door closing nearly the whole year. Range hood usage accompanied with opening kitchen window was the most popular ventilation mode in kitchen. Indoor UFPs were presented with concentration level of 9799 +/- 5036 counts/cm3 in winter, significantly higher than that in summer (6655 +/- 2707 counts/cm3) and transition season (6230 +/- 1710 counts/cm3), and sharply fluctuated with cooking activities. During the non-cooking periods, however, UFPs in living room and bedroom were mostly derived from outdoors (68.99%-96.95%) in summer and indoors (79.33%-85.66%) in winter. Further quantitative analysis indicates that the emission rate in the monitored kitchens was 0.693 +/- 1.215 x 1013 counts/min in the whole process of cooking, greatly depended on the cooking methods and dish menus. The study could be a reference of better understanding impacts of occupant behaviors on indoor UFP pollution in residential buildings.

Automated summary

The study found that outdoor air temperature is a key factor influencing occupants' window-opening behaviors in residences, with most preferring to use range hood accompanied by opening kitchen window for ventilation. Indoor UFP concentrations were significantly higher in winter compared to summer and transition season, correlating with cooking activities.