Evaluation of the filtration performance of NIOSH-approved N95 filtering facepiece respirators by photometric and number-based test methods

Details

• Personal Author:
  Eimer BC ; Miller, Aubrey K. ; Rengasamy S
• Description:
  N95 particulate filtering facepiece respirators are certified by measuring penetration levels photometrically with a presumed severe case test method using charge neutralized NaCl aerosols at 85 L/min. However, penetration values obtained by photometric methods have not been compared with count-based methods using contemporary respirators composed of electrostatic filter media and challenged with both generated and ambient aerosols. To better understand the effects of key test parameters (e.g., particle charge, detection method), initial penetration levels for five N95 model filtering facepiece respirators were measured using NaCl aerosols with the aerosol challenge and test equipment employed in the NIOSH respirator certification method (photometric) and compared with an ultrafine condensation particle counter method (count based) for the same NaCl aerosols as well as for ambient room air particles. Penetrations using the NIOSH test method were several-fold less than the penetrations obtained by the ultrafine condensation particle counter for NaCl aerosols as well as for room particles indicating that penetration measurement based on particle counting offers a more difficult challenge than the photometric method, which lacks sensitivity for particles < 100 nm. All five N95 models showed the most penetrating particle size around 50 nm for room air particles with or without charge neutralization, and at 200 nm for singly charged NaCl monodisperse particles. Room air with fewer charged particles and an overwhelming number of neutral particles contributed to the most penetrating particle size in the 50 nm range, indicating that the charge state for the majority of test particles determines the MPPS. Data suggest that the NIOSH respirator certification protocol employing the photometric method may not be a more challenging aerosol test method. Filter penetrations can vary among workplaces with different particle size distributions, which suggests the need for the development of new or revised "more challenging" aerosol test methods for NIOSH certification of respirators. [Description provided by NIOSH]
• Subjects:
  Aerosols Air Pollutants, Occupational Filtration Occupational Health Particulate Matter Personal Protective Equipment Respiratory Protective Devices Safety
• Keywords:
  Aerosol-generators Aerosol-particles Air-filters Air-purifying-respirators Author Keywords: More Challenging Aerosol Detectors Electrostatic-filters Face-masks Filters N95 Respirator NaCl Aerosol NIOSH Certification Test Particle-counters Particulates Penetration Photometry Respirators Room Air Aerosol Testing-equipment

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• ISSN:
  1545-9624
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  OSHA Region 3 ; Pennsylvania
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  NPPTL - National Personal Protective Technology Laboratory
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  23-30
• Volume:
  8
• Issue:
  1
• NIOSHTIC Number:
  nn:20038084
• Citation:
  J Occup Environ Hyg 2011 Jan; 8(1):23-30
• Contact Point Address:
  Samy Rengasamy, National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, 626 Cochrans Mill Road, P.O.Box 18070, Pittsburgh, PA 15236
• Email:
  ARengasamy@cdc.gov
• Federal Fiscal Year:
  2011
• Peer Reviewed:
  True
• Source Full Name:
  Journal of Occupational and Environmental Hygiene
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:b3210913b7bbf1cbef8f33e02a5ef283e924ced86c13f7cbffbb5d0748be4a96b7689c679ae9ce2f63a236d7525ed729ff4a88ae368c338fc3efeb0e148a78c9
• Download URL:
  https://stacks.cdc.gov/view/cdc/191902/cdc_191902_DS1.pdf
• File Type:
  [PDF - 501.03 KB ]