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The Relationship between Breathing Zone Concentration and Capture Efficiency.
Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina 1990 Feb:7 pages
The theory was presented that if a worker's breathing zone concentration were proportional to the average room concentration at a given time, then the breathing zone concentration at that time should be directly proportional to the contaminant flow rate and inversely proportional to the time averaged capture efficiency. This theory was examined experimentally with a mannequin and several local exhaust hoods. The results suggested that the time integral of capture efficiency is inversely proportional to the instantaneous breathing zone concentration. The use of capture efficiency as a design parameter appeared superior to the capture velocity concept in that a stronger relationship exists with the parameter of interest, that is, the exposure. The author concludes that the difficulty in predicting capture efficiency for actual operation makes its use in modelling questionable. One may as well simulate the concentration directly. However, its true potential for application lies in monitoring and measurement since duct concentrations are easily obtained. Further study is needed to confirm the functional relationship for more realistic laboratory simulations and field studies. It is important that the time integral of the efficiency be used and that the start up of the operation be included since efficiencies tended to approach 100% rather quickly.
NIOSH-Grant; Control-technology; Ventilation-systems; Air-quality-control; Air-quality-monitoring; Toxic-gases;
Environmental Sciences & Engr University of North Carolina Rosenau Hall 201H Chapel Hill, NC 27514
Final Grant Report;
NTIS Accession No.
Control Technology and Personal Protective Equipment; Research Tools and Approaches; Control-technology;
Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina
University of North Carolina Chapel Hill, Chapel Hill, North Carolina
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division