Characterizing and modeling close-proximity exposure to an air pollution source in naturally ventilated residences

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Near an active indoor emission source, air pollutant levels are elevated and highly-variable, due to non-instantaneous mixing -- this causes great uncertainty in estimating a person's exposure level. This research investigated the magnitude and variability of short-term exposures close to an active point source inside 2 homes, under a range of natural ventilation conditions. The findings from a newly-developed monitor signal reconstruction method were applied to measurements from 30-37 real-time monitors to capture the spatial and temporal variations of concentrations over 30-min CO tracer gas releases. For 11 experiments involving 2 houses, with natural ventilation conditions ranging from < 0.2 to > 5 air changes per h, an eddy diffusion model was used to determine the turbulent diffusion coefficients. The air change rate showed a significant positive linear correlation with the air mixing rate, defined as the turbulent diffusion coefficient divided by a squared length scale representing the room size. To predict the magnitude of exposure close to an active source, an indoor dispersion model was formulated, invoking the theory of random walk, and incorporating the physical processes of anisotropic turbulent diffusion, removal of the air pollutant, and air pollutant wall reflection. Then, to capture the variability of concentrations in close proximity to an active source, a new piece-wise random walk algorithm was developed to stochastically simulate the transient directionality of emitted plume. The distribution of different exposure cases generated using this model reasonably covered the range of experimental measurements collected in 2 houses, while preserving ensemble averages satisfying the principle of Fickian diffusion.


Type of resource text
Form electronic; electronic resource; remote
Extent 1 online resource.
Copyright date 2011
Publication date 2010, c2011; 2010
Issuance monographic
Language English


Associated with Cheng, Kai-Chung
Associated with Stanford University, Civil & Environmental Engineering Department
Primary advisor Hildemann, Lynn M. (Lynn Mary)
Thesis advisor Hildemann, Lynn M. (Lynn Mary)
Thesis advisor Fringer, Oliver B. (Oliver Bartlett)
Thesis advisor Kitanidis, P. K. (Peter K.)
Advisor Fringer, Oliver B. (Oliver Bartlett)
Advisor Kitanidis, P. K. (Peter K.)


Genre Theses

Bibliographic information

Statement of responsibility Kai-Chung Cheng.
Note Submitted to the Department of Civil and Environmental Engineering.
Thesis Thesis (Ph.D.)--Stanford University, 2011.
Location electronic resource

Access conditions

© 2011 by Kai-Chung Cheng
This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).

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