Annals of Occupational Hygiene Advance Access originally published online on December 16, 2004
Annals of Occupational Hygiene 2005 49(1):61-71; doi:10.1093/annhyg/meh078
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© 2004 British Occupational Hygiene Society Published by Oxford University Press;
Applying Open-Path FTIR with Computed Tomography to Evaluate Personal Exposures. Part 1: Simulation Studies
1 Department of Environmental and Occupational Health Sciences, Box 357234, University of Washington, Seattle, WA 98195; 2 ARCADIS, PO Box 13109, Research Triangle Park, NC 27709; 3 Department of Civil and Environmental Engineering, Box 352700, University of Washington, Seattle, WA 98195; 4 Department of Industrial and Management Systems Engineering, West Virginia University, Morgantown, WV 26506, USA
* Author to whom correspondence should be addressed. Fax: +1-206-543-8123; e-mail: cfwu{at}u.washington.edu
This paper presents the theoretical background and the numerical evaluation results obtained using computed tomography coupled with open-path Fourier transform infrared (CT-FTIR) measurements to estimate personal exposures. In this simulation study, we first tested the one-dimensional scenario with a five-beam segment geometry. A series of Gaussian plumes and the corresponding path-integrated concentrations (PICs) were simulated. The personal exposures were estimated as the average of the point estimates calculated from the workers' locations and the concentration profiles reconstructed from the Smooth Basis Function Minimization algorithm. It was found that the running-average PIC updating strategy has similar performance as the spline PIC updating strategy. However, the latter strategy gives delayed estimates of the workers' exposures since it requires additional measurements before and after the time period of interest. In the two-dimensional scenario, we simulated a series of single-mode bivariate Gaussian plumes with a nine-beam radial geometry. The average of the estimated exposures from the CT-FTIR approach was close to the average of the true exposures. The concordance correlation factors between the true and estimated exposures were reasonably good (between 0.50 and 0.58). This study demonstrated that the CT-FTIR approach is feasible for industrial hygiene monitoring.
Keywords: computed tomography • open-path FTIR • optical remote sensing • personal exposure • radial plume mapping