Contribution of Non-HEPA Preliminary Filters to the Efficiency and Life-Span of HEPA Filters In Reducing Cadmium Contaminated Emissions and Respirable Particles

Details

• Personal Author:
  Akbar-Khanzadeh F ; Smigielski K
• Description:
  Objective: Pre-filtering media, such as non-HEPA filters, are often installed in front of HEPA filters with the expectation that they will improve efficiency of particle removal, expand the life cycle of the HEPA filters and reduce the cost of filtration. This study was conducted in four manufacturing processes to examine these expectations. Methods: The concentration of cadmium contaminated emission (Cd) as well as size distribution of these particles were determined in five locations: area in the shop immediately in front of air intake to the process (Intake); the inlet of the ventilation system to establish the uncontrolled emission levels from the process before pre (primary)-filter (Inlet); between the pre-filter and HEPA filter to quantify the effectiveness of the primary filtration (Between); immediately after the HEPA filter (Outlet) to determine overall effectiveness; and, in the shop area in front of air discharge to the shop (Discharge). The respirable particles were only sampled at Inlet, Between and Outlet locations. The particles were also monitored using a five-stage dust impactor, a particle counter and a ventilation airflow meter. Experiment continued over days until the HEPA filters became technically inefficient. The air samples were collected multiple times at each location. Results: The mean (SD) of Cd contaminated emission at the five monitoring locations were as follow: Intake 0.49 (0.16) ug/m3; Inlet (after process) 62.6 (158) ug/m3; Between 4.9 (14.1) ug/m3; Outlet 0.01 (0.03) ug/m3; and, Discharge 0.20 (0.08) ug/m3. The mean (SD) of respirable particles were measured as follow: Inlet 556 (1085) ug/m3; Between 26.9 (68.8) ug/m3; Outlet 0.55 (0.83) ug/m3. On average, efficiency of the prefilter was 92.2 percent for Cd and 95.2 percent for respirable particles, leaving 7.8 percent of Cd and 4.8 percent of respirable particles to be captured by the HEPA filter. The size distribution of particle were almost even at the five size (um) channels of >2.5, 1.0 - 2.5, 0.5 - 1.0, 0.25 - 0.5, and <0.25, with higher levels at 1-2.5 um size. Conclusions: This study indicates that though the capture efficiency of a pre-filter is not remarkably high (92.2 percent for Cd), but it has a fundamental support in increasing the life expectancy of HEPA filter, reducing the cost and increasing operational efficiency of the ventilation system which leads to less downtime of the process. [Description provided by NIOSH]
• Subjects:
  Air Pollutants, Occupational Occupational Health Particulate Matter Safety Ventilation
• Keywords:
  Airborne Particulates Air Filters Cadmium Dust Filter Materials HEPA Filters High-efficiency Particulate Air Filters
• Publisher:
  American Industrial Hygiene Association
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  Ohio ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  13-14
• NIOSHTIC Number:
  nn:20054443
• Citation:
  AIHce 2014: American Industrial Hygiene Conference and Exposition, May 31 - June 5, 2014, San Antonio, Texas. Falls Church, VA: American Industrial Hygiene Association, 2014 Jun; :13-14
• CAS Registry Number:
  Cadmium (CAS RN 7440-43-9)
• Federal Fiscal Year:
  2014
• Performing Organization:
  University of Toledo Health Science Campus, Ohio
• Peer Reviewed:
  False
• Start Date:
  20050701
• Source Full Name:
  AIHce 2014: American Industrial Hygiene Conference and Exposition, May 31 - June 5, 2014, San Antonio, Texas
• End Date:
  20250630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:0d49f76b5ccd10d240ea1ed25f2e30b82c8d5da59138c9f475083ce96b3f53c9c77beea8256282a492569e269dbf8f6e9d1bb96538699afb62681730e87b42d0
• Download URL:
  https://stacks.cdc.gov/view/cdc/217009/cdc_217009_DS1.pdf
• File Type:
  [PDF - 333.08 KB ]