SPATIAL AND TEMPORAL VISUALIZATION OF GASES AND VAPORS IN AIR USING COMPUTED-TOMOGRAPHY - NUMERICAL-STUDIES

Numerical studies were performed to evaluate a new method for human ex posure assessment and source monitoring, based upon optical remote sen sing (ORS) and computed tomography (CT). With an ORS-CT system, two-di mensional maps of chemical concentrations in air, with good spatial an d temporal resolution, can be created over a confined space such as a workplace room. The ORS-CT system was evaluated using 15 simulated tes t maps that model the generation and dispersion of contaminant plumes over time. A program simulated field measurements from these maps assu ming different remote sensing scan times. Using these measurements, re constructed maps were generated and compared with original maps. Quali tative and quantitative methods were used to evaluate the effect on re construction quality of sample time, number of iterations used by the maximum likelihood expectation maximization reconstruction algorithm a nd sample density. For this study, scanning an entire room in 10 min w as adequate for exposure evaluation, source monitoring and leak detect ion. (C) 1997 British Occupational Hygiene Society.