EVALUATION OF OPTICAL SOURCE-DETECTOR CONFIGURATIONS FOR TOMOGRAPHIC RECONSTRUCTION OF CHEMICAL CONCENTRATIONS IN INDOOR AIR

This article reports on numerical studies to evaluate and compare opti cal remote sensing configurations for tomographically, reconstructing pollutant concentrations in indoor air. With a remote sensing/computed tomography system, two-dimensional maps of pollutant concentrations w ith good spatial resolution can be created for an entire room. The suc cessful use of such a system for exposure assessment, ventilation asse ssment, or source monitoring depends on the remote sensing configurati on. A systematic method was developed to evaluate the performance of l o configurations. One hundred and twenty test maps were reconstructed with an algebraic reconstruction method using all 10 configurations; r econstruction qualify was evaluated using 4 criteria. Reconstruction q uality was related to the number and location of detectors in the room and the complexity of the test maps. Configurations using the same nu mber of detectors placed in different locations resulted in reconstruc tions chat differed in quality. The effect of reducing the number dens ity of rays on reconstruction quality was studied Based on these simul ations, two configurations that used four detectors to scan the room w ere selected and their performance was evaluated in the presence of va rious levers of measurement noise. Two configurations that used four d etectors were most suited for exposure assessment. It was found that w hen designing a configuration, the number and independence of rays sho uld be maximized. Results underscored the need to thoroughly test conf igurations through numerical studies prior to field implementation; a wide variety of concentration maps, relevant to the application, shoul d be tested under both ideal and nonideal sampling conditions.