Significant Cross-Contamination Caused by Cooking Fume Transport between Dwelling Units in Multilayer Buildings

Cross-contamination in multiunit residential buildings is an inevitable but poorly studied issue. We conducted a 2-month monitoring campaign in a multilayer residential building, identifying 53 interunit kitchen exhaust transmission events (∼2 per day), causing enhanced exposure of particulate matters (PM), black carbon (BC), NO x, and CO and volatile organic compounds (VOCs) in both the kitchen and living room. These events resulted in a 40–80% increase in PM deposition in the respiratory systems for occupants in the living room, especially fine particles depositing in the alveolar region. Evidence indicates that these pollutant events originated from cooking fume transport. The geometric mean diameter of kitchen particles decreased from 76 nm during background periods to 62 nm during transport events, consistent with smaller PM from cooking activities. Furthermore, 30 cooking-related VOCs were identified as transport indicators, including hazardous species such as aldehydes. We confirmed that leakage of cooking fume through the shared kitchen exhaust duct led to cross-contamination, which can be effectively mitigated by using exhaust hoods, air cleaners, or opening windows during mealtimes. This research provides the first quantitative assessment of cooking emission transport between dwellings in multilayer housing, highlighting the significant impact of cross-contamination in high-density residential environments.