NIOSHTIC-2 Publications Search

Optical remote sensing and computed tomography.

Todd L
Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 1994 Dec; :1-65
A final performance report was presented on the feasibility of determining gas or vapor concentration in a room by combining optical remote sensing with computed tomography. Detailed results of optical remote sensing configurations, placement of light sources and detectors in a room were summarized. The quality of reconstruction of concentration maps was related to the number and location of the detectors and the complexity of the concentration profiles. A configuration using four detectors in a 180 degree configuration gave the best nearness and data distance values of the ten configurations tested. This configuration was able to reconstruct maps with up to six concentration peaks and with the introduction of up to 10% measurement noise. Use of only 50% or 25% of the rays also resulted in good reconstruction quality. Sulfur- hexafluoride (SF6) path averaged concentration measurements with an INFRASAFE open path spectrometer, using either single or reflected beam configurations, were not significantly different from analysis of point samples with an infrared spectrophotometer or electron capture detector. Open path spectrometer measurements of heterogenous concentrations were within 20% of point sample measurements obtained with an electron capture detector. A Midac bistatic open path Fourier Transform Infrared Spectrometer (FTIR) measured SF6 concentrations to within 15% of the generated concentrations. Several virtual scanning spectrometers were simulated by mounting the FTIR on a motorized track in the test chamber. This system accurately reconstructed concentration maps of SF6 peak locations. The accuracy was reduced by the slow sampling time of the system and varied with the chamber injection site. This was especially evident when turbulence was introduced in the test chamber. The usefulness of the findings were discussed. Two previous publications were included at the end of the performance report. The author concludes that, with reduced sampling time, this system could be used to evaluate exposures and map air flows in the workplace.
NIOSH-Grant; Grants-other; Air-monitoring; Air-quality-measurement; Air-quality-monitoring; Infrared-spectrophotometry; Measurement-equipment; Analytical-methods
Environmental Sciences & Engr University of North Carolina CB #7400 Chapel Hill, NC 27599-7400
Publication Date
Document Type
Final Grant Report
Funding Amount
Funding Type
Fiscal Year
Identifying No.
NIOSH Division
Priority Area
Other Occupational Concerns; Grants-other
Source Name
Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina
Performing Organization
University of North Carolina Chapel Hill, Chapel Hill, North Carolina
Page last reviewed: February 25, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division