STATIONARY AND TIME-DEPENDENT INDOOR TRACER-GAS CONCENTRATION PROFILES MEASURED BY OP-FTIR REMOTE-SENSING AND SBFM-COMPUTED TOMOGRAPHY

Measurement of gas concentrations in indoor air using optical remote s ensing (ORS) and computed tomography (CT) has been suggested but not t horoughly investigated. We present experiments in which one time-varyi ng and 11 different steady-state tracer-gas concentration profiles wer e generated in a ventilated chamber and sampled in a horizontal plane by an open-path Fourier transform infrared (OP-FTIR) spectrometer for subsequent CT inversion. CT reconstructions were performed using the r ecently developed smooth basis function minimization (SBFM) technique. The CT reconstructions were compared with simultaneously gathered poi nt-sample concentration measurements. Agreement between the two sampli ng methods was qualitatively very good, with concentration profiles ge nerated by both methods showing the same features of peak location and shape. Quantitative agreement was generally good to within 50%. We di scuss the sources of discrepancy and suggest directions for future res earch, especially with regard to monitoring time-dependent processes. With further refinements in the SBFM algorithm and improvements in opt ical remote sensing hardware, this technique promises to yield rapid a nd accurate measurements of the spatial distribution of gases in indoo r environments. Copyright (C) 1996 Elsevier Science Ltd.