Indoor air pollutant concentrations can be influenced by how rapidly species are transported to and from surfaces. Consequently, a greater understanding of indoor transport phenomena to surfaces improves estimates of human exposure to indoor air pollutants. Here, we introduce two methods of rapidly and directly measuring species fluxes at indoor surfaces, allowing us to evaluate the transport-limited deposition velocity, vt (a mass-transfer coefficient). The deposition velocity sensor (DeVS) method employs a small microbalance coated with a pure hydrocarbon, preferably octadecane. We quantify flux (or evaporation rate) of the hydrocarbon into a room by observing the rate of mass loss on the microbalance. The transport-limited deposition velocity, vt, octadecane, is then obtained by combining the flux with the vapor pressure of the hydrocarbon. Simultaneously, vt, ozone is quantified using the depostion velocity of ozone (DeVO) method, which acts as a standard to caliberate ans evaluate DeVS. Specifically, DeVO evaluates ozone transport to surfaces by quantifying the conversion by ozone of nitrate on a glass fiber filter. Simultaneous laboratory chamber experiments demonstrates that vt for octadecane and ozone are strongly correlated, with the values for ozone ~1.5 times greater than that for octadecane. In an office experiments, the DeVS method responds within minutes to step changes in conditions such as occupancy, activities and ventilation. At present, the results are in order-of-magnitude agreement with predicted indoor mass-transfer coefficients.
G. Morrison et al., "Rapid Measurement of Indoor Mass-Transfer Coefficients," Atmospheric Environemnt, Elsevier Ltd., Jan 2003.
The definitive version is available at http://dx.doi.org/10.1016/j.atmosenv.2003.09.034
Civil, Architectural and Environmental Engineering
Missouri State University
Keywords and Phrases
Deposition Velocity; Indoor air; Microbalance; Ozone; Pollutant transport
Article - Journal
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