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Dependence of particulate sampling effeciency on inlet orientation and flow velocities.
Am Ind Hyg Assoc J 1982 Jun; 43(6):436-443
An airborne particulate sampler inlet was studied for sampling efficiency through the use of a wind tunnel apparatus. Liquid particles entering the inlet were registered on an optical particle counter. The magnitude of particle deposition in the inlet tube was obtained with a uranine labelled oleic-acid aerosol and washoff that related the fluorescence to the number of deposited particles. Liquid particles of oleic acid ranged in diameter from 5 to 40 micrometers. Wind velocity varied from 250 to 1000 centimeters per second (cm/s) and the inlet velocity varied from 125 to 1000cm/s. The inlet was tested isoaxial to the wind at angles 0 to 30 degrees, with the optical counter inside the wind tunnel. At angles 60 to 90 degrees the counter was inside the tunnel. Wind tunnel turbulence of a few percent had no effect on sampling efficiency. Particle aspiration to the inlet face affected small particle isoaxial sampling, while gravitational sedimentation in the horizontal inlet tube was the removal mechanism for large particles. Downward air sampling resulted in higher sampling efficiency than upward sampling for particle size above 10 micrometers. The effect of gravity on sampling efficiency was most pronounced between upward angle 15 degrees and downward 15 degrees. Gravity became less important with increase in angle. As orientation of the inlet angled away from the wind vector, lack of aspiration increased both particle loss and particle impaction just inside the inlet face.
NIOSH-Publication; NIOSH-Grant; Analytical-methods; Laboratory-techniques; Air-sampling-equipment; Air-monitoring; Air-quality-measurement; Equipment-design; Analytical-instruments; Sampling-equipment
Environmental Health University of Cincinnati 3223 Eden Avenue Cincinnati, Ohio 45267
Issue of Publication
American Industrial Hygiene Association Journal
University of Cincinnati, Cincinnati, Ohio
Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division