Technical issues associated with innovative environmental technology: FTIR computer-aided tomography

This research reports on a new innovation in chemical measurement technology that combines open-path Fourier transform infrared (OP-FTIR) spectroscopy with computed tomography to create two-dimensional maps of air contaminants that are both spatially and temporally resolved. This method has been evaluated with numerical studies that tested different iterative reconstruction algorithms and OP-FTIR configurations. The success of this system for characterizing the flow of contaminants in air, exposure assessment, emission monitoring and leak detection, was closely linked to the choice of reconstruction algorithm and configuration. A systematic method was developed to evaluate these parameters using static and time series test maps under ideal and non-ideal sampling conditions. Concentration map quality was evaluated using qualitative and quantitative criteria. Map reconstruction quality using different algorithms and configurations was found to be intimately related to the complexity of the test maps. The results of this research underscore the need to thoroughly test the system through numerical studies prior to field implementation; a wide variety of concentration maps, relevant to the application, should be tested under both ideal and non-ideal sampling conditions.