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THE USE OF BOX MODELS TO DESCRIBE THE PERSONAL CLOUD EFFECT ON HUMAN EXPOSURE TO PARTICULATE MATTER
Citation:
Heist, D. K., A. D. Eisner, W J. Mitchell, AND R W. Wiener. THE USE OF BOX MODELS TO DESCRIBE THE PERSONAL CLOUD EFFECT ON HUMAN EXPOSURE TO PARTICULATE MATTER. Presented at American Association for Aerosol Research, Portland, OR, October 15-19, 2001.
Impact/Purpose:
The objective of this task is to develop and employ PM measuring tools for EPA researchers and regulators to use to characterize the exposure of humans to PM of outdoor origin in both outdoor and indoor environments. Achieving these objectives will improve the scientific foundation for risk assessments of PM in future reevaluations of the NAAQS and in assessing exposure of humans to PM.
Description:
An algorithm has been developed to describe particle transport into and out of the breathing zone in an effort to predict the effects of the personal cloud phenomenon (Eisner and Heist, 2000). The algorithm was developed based on the principle of mass balance between a system of well-mixed zones (or boxes) with flow between them. The algorithm was used to model breathing-zone concentrations around a child-size manikin used in wind tunnel experiments.
We propose a three-box model, where the smallest of the boxes represents a local source of particulate matter, the medium-size box represents a personal cloud space, and the largest box represents the rest of the room. By dividing the volume of a room into three sub-volumes, each characterized by a specific airflow through it, we can limit the assumption of the well-mixed conditions to a much smaller volume, thus improving overall model performance.
Experimental measurements of air velocity and aerosol concentration around a child-size manikin have been used to estimate the parameters used in the algorithm. The size of the boxes depends on the flow patterns around the body and vary depending on the simulated conditions in the wind tunnel. The flow rates between the boxes were estimated from the velocity field measurements. The source characteristics were obtained from experiments with pre-loaded surfaces.
The algorithm has been tested with data produced from a wind tunnel experiment where a floor level release of aerosol was entrained into the breathing zone by the natural convection caused by the manikin's simulated body heat. Initial model results compare favorably with the experimental results. The reliability of the algorithm is also being verified in unsteady conditions through comparison with laboratory data.
This abstract has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.