The long-term performance of electrically charged filters in a ventilation system.
J Occup Environ Hyg 2004 Jul; 1(7):463-471
The efficiency and pressure drop of filters made from polyolefin fibers carrying electrical charges were compared with efficiency and pressure drop for filters made from uncharged glass fibers to determine if the efficiency of the charged filters changed with use. Thirty glass fiber filters and 30 polyolefin fiber filters were placed in different, but nearly identical, airhandling units that supplied outside air to a large building. Using two kinds of real-time aerosol counting and sizing instruments, the efficiency of both sets of filters was measured repeatedly for more than 19 weeks while the air-handling units operated almost continuously. Pressure drop was recorded by the ventilation system's computer control. Measurements showed that the efficiency of the glass fiber filters remained almost constant with time. However, the charged polyolefin fiber filters exhibited large efficiency reductions with time before the efficiency began to increase again toward the end of the test. For particles 0.6 umin diameter, the efficiency of the polyolefin fiber filters declined from 85% to 45% after 11 weeks before recovering to 65% at the end of the test. The pressure drops of the glass fiber filters increased by about 0.40 in. H2O, whereas the pressure drop of the polyolefin fiber filters increased by only 0.28 in. H2O. The results indicate that dust loading reduces the effectiveness of electrical charges on filter fibers.
Aerosol-particles; Aerosols; Airborne-particles; Air-contamination; Bacteria; Bacterial-disease; Bacterial-dusts; Bacterial-infections; Biological-effects; Cell-biology; Demographic-characteristics; Engineering; Engineering-controls; Environmental-exposure; Environmental-factors; Environmental-hazards; Environmental-health; Exposure-assessment; Exposure-levels; Exposure-methods; Immune-reaction; Immune-system; Inhalants; Inhalation-studies; Personal-protection; Physiological-effects; Physiological-factors; Physiological-response; Pollution; Protective-equipment; Protective-measures; Public-health; Quantitative-analysis; Risk-analysis; Risk-factors; Safety-measures; Safety-practices; Statistical-analysis; Surface-properties; Water-analysis; Work-environment; Workplace-studies; Work-practices;
Author Keywords: air filtration; dust loading; efficiency; electrostatics; filters; ventilation
Peter Raynor, Division of Environmental Health Sciences, University of Minnesota, Mayo Mail Code 807, 420 Delaware Street S.E., Minneapolis, MN 55455
Journal of Occupational and Environmental Hygiene
University of Minnesota Twin Cities