Development of a prototype rapid scanning CAT-FTIR industrial imaging system for tomographic mapping of indoor air contaminants

Current techniques for evaluating exposures in indoor air typically involve integrated sampling for a limited number of workers and locations; this results in measurements which are limited in both space and time. A technique is being developed for exposure assessment which is a major departure from currently used techniques and involves Computer Assisted Tomography-Fourier Transform Infrared (CAT-FTIR) scanning of a room. Using this method, the concentration and location of chemicals in air could be mapped in real-time over an entire room; thus, a video of both spatially and temporally resolved chemical concentrations could be created.; This research develops and tests a prototype CAT-FTIR Industrial Imaging System. Open path FTIR (OP-FTIR) spectroscopy is employed to scan a room, in one plane, creating a network of intersecting optical paths. The individual path-integrated concentrations obtained are processed by a tomographic algorithm, to reconstruct and produce a two-dimensional map of the chemical concentration distribution in the room.; Although OP-FTIR spectroscopy technology is gaining acceptance in the environmental field, there has not yet been a comprehensive assessment of instrument performance and the analytical limitations of this method have not been thoroughly delineated. An investigation into the use of a custom-designed continuous flow external calibration cell as a tool for validation of an OP-FTIR spectrometer was performed along with commonly used performance parameters. Methods for calibrating OP-FTIR spectrometers were developed using a custom designed external gas calibration cell to provide guidance into quality assurance/quality control parameters.; The impact of test maps on the validation of the CAT-FTIR tomographic reconstructions was demonstrated. Tomographic reconstructions of single and multiple plumes of sulfur hexafluoride were evaluated on the basis of peak location and concentration.; Preliminary evaluation of the industrial CAT-FTIR scanning system suggests it shows potential as a viable method for mapping indoor chemical contaminants. This non-invasive, portable, easy to calibrate, and completely computer controlled system scanned a small room in about seven minutes providing near real-time contaminant concentration maps and was able to locate peaks within one foot of the actual location.