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Aerosol penetration through surgical masks

  • Author Footnotes
    * Current address: Division of Physical Science and Engineering, National Institute for Occupational Safety and Health, Cincinnati, OH 45226.
    Chih-Chieh Chen
    Footnotes
    * Current address: Division of Physical Science and Engineering, National Institute for Occupational Safety and Health, Cincinnati, OH 45226.
    Affiliations
    From the Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio., USA
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  • Klaus Willeke
    Correspondence
    Reprint requests: Klaus Willeke, PhD, Aerosol Research and Respiratory Protection Laboratory, Department of Environmental Health, University of Cincinnati Medical Center, Cincinnati, OH 45267-0056.
    Affiliations
    From the Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio., USA
    Search for articles by this author
  • Author Footnotes
    * Current address: Division of Physical Science and Engineering, National Institute for Occupational Safety and Health, Cincinnati, OH 45226.
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      Abstract

      Background:

      Surgical masks are used in hospitals to reduce postoperative infection in patients. The presence of aerosols containing pathogens makes it desirable to protect the medical staff as well.

      Methods:

      The collection efficiencies of surgical masks were measured with two aerosol-size spectrometers. The flow rates through the masks were varied from 5 to 100 L/min to study the flow dependency. For comparison, several industrial-type respirators were also tested.

      Results:

      A surgical mask consisting of filter material performed better than did a surgical mask consisting only of a shell with a coarse pore structure. The latter passed 80% of submicrometer-sized aerosols with little flow dependency, whereas the penetration of submicrometer-sized aerosols through the mask made of filter material ranged from 25% at a flow rate of 5 L/min to 70% at 100 L/min.

      Conclusions:

      The mask that has the highest collection efficiency is not necessarily the best mask from the perspective of the filter-quality factor, which considers not only the capture efficiency but also the air resistance. Although surgical mask media may be adequate to remove bacteria exhaled or expelled by health care workers, they may not be sufficient to remove the submicrometer-sized aerosols containing pathogens to which these health care workers are potentially exposed.

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