Mapping air contaminants indoors using a prototype computed tomography system

Single and multiple plumes of sulphur hexafluoride were measured and mapped using a prototype open-path Fourier transform infrared spectrometer (OP-FTIR)-computed tomography (CT) system in an indoor exposure chamber. The OP-FTIR-CT system accurately mapped the position of concentration peaks at different locations in the chamber, and estimated concentrations within a range of 4-50% when compared with point samples measured by gas chromatography with an electron capture detector. Two OP-FTIR spectrometer ray configurations, one with 100 rays and the other with 136 rays, were used to scan the chamber and reconstruct the concentration maps. Ray configuration and time to scan the entire chamber were found to have a profound effect on the quality of the reconstructed maps. The ability to obtain real-time, non-invasive measurements, and to generate spatially and temporally resolved maps of multiple chemicals, makes the OP-FTIR-CT system a promising technique for monitoring source emissions and evaluating exposures to air contaminants in a workplace.