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Particle Mass Concentrations and Number Size Distributions in 40 Homes in Germany: Indoor-to-outdoor Relationships, Diurnal and Seasonal Variation

Category: Urban Air Quality

Volume: 20 | Issue: 3 | Pages: 576-589
DOI: 10.4209/aaqr.2019.09.0444
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To cite this article:
Zhao, J., Birmili, W., Wehner, B., Daniels, A., Weinhold, K., Wang, L., Merkel, M., Kecorius, S., Tuch, T., Franck, U., Hussein, T. and Wiedensohler, A. (2020). Particle Mass Concentrations and Number Size Distributions in 40 Homes in Germany: Indoor-to-outdoor Relationships, Diurnal and Seasonal Variation. Aerosol Air Qual. Res. 20: 576-589. doi: 10.4209/aaqr.2019.09.0444.

Jiangyue Zhao1, Wolfram Birmili2, Birgit Wehner1, Anja Daniels2, Kay Weinhold1, Lina Wang4, Maik Merkel1, Simonas Kecorius1, Thomas Tuch1, Ulrich Franck3, Tareq Hussein5,6, Alfred Wiedensohler 1

  • 1 Leibniz Institute for Tropospheric Research, 04318 Leipzig, Germany
  • 2 German Environment Agency (UBA), 14195 Berlin, Germany
  • 3 Helmholtz Centre for Environmental Research, 04318 Leipzig, Germany
  • 4 Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
  • 5 University of Jordan, Amman 11942, Jordan
  • 6 Institute for Atmospheric and Earth System Research, University of Helsinki, 00560 Helsinki, Finland


  • Size-resolved investigation of residential exposure to 10 nm–10 µm size particles.
  • Representative exposure diurnal pattern in multiple homes in over 500 days.
  • Indoor exposures to coarse particles were roughly double to outdoors.
  • Indoor particle number concentrations were driven by outdoors (I/O ratio 0.7).
  • The German homes are relatively airtight (median penetration factor 0.3–0.5).


Few studies investigated residential particle concentration levels with a full picture of aerosol particles from 10 nm to 10 µm size range with size-resolved information, and none was performed in central Europe in the long-term in multiple homes. To capture representative diurnal and seasonal patterns of exposure to particles, and investigate the driving factors to their variations, measurements were performed in 40 homes for around two weeks each in Leipzig and Berlin, Germany. These over 500 days’ measurements combined PM10 and PM2.5 mass concentrations, particle number concentration and size distribution (PNC and PNSD, 10–800 nm), CO2 concentration, and residential activities diary into a unique dataset. Natural ventilation was dominated, the mean ventilation rate calculated from CO2 measurements was 0.2 h–1 and 3.7 h–1 with closed and opened windows, respectively. The main findings of this study showed that, the residents in German homes were exposed to a significantly higher mass concentration of coarse particles than outdoors, thus indoor exposure to coarse particles cannot be described by outdoors. The median indoor PNC diurnal cycles were generally lower than outdoors (median I/O ratio 0.69). However, indoor exposure to particles was different in the cold and warm season. In the warm season, due to longer opening window periods, indoor sources’ contribution was weakened, which also resulted in the indoor PNC and PNSD being very similar to the outdoors. In the cold season, indoor sources caused strong peaks of indoor PNC that exceeded outdoors, along with the relatively low penetration factor - 0.5 for all size ranges, and indoor particle losses, which was particularly effective in reducing the ultrafine PNC, resulting in a different particle exposure load than outdoors. This study provides a detailed understanding of residential particle exposure in multiple homes, facilitating future studies to assess health effects in residential environments.


Indoor particle exposure Indoor particle loss Indoor source I/O ratio Penetration

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