Skip to main content

Main menu

  • Home
  • Content
    • Current issue
    • Past issues
    • Early releases
    • Collections
    • Sections
    • Blog
    • Infographics & illustrations
    • Podcasts
    • COVID-19 articles
    • Obituary notices
  • Authors & Reviewers
    • Overview for authors
    • Submission guidelines
    • Submit a manuscript
    • Forms
    • Editorial process
    • Editorial policies
    • Peer review process
    • Publication fees
    • Reprint requests
    • Open access
    • Patient engagement
  • Physicians & Subscribers
    • Benefits for Canadian physicians
    • CPD Credits for CMA Members
    • Subscribe to CMAJ digital
    • Subscribe to CMAJ print
    • Subscription prices
    • Obituary notices
  • Alerts
    • Email alerts
    • RSS
  • JAMC
    • À propos
    • Numéro en cours
    • Archives
    • Sections
    • Abonnement
    • Alertes
    • Trousse média 2023
    • Avis de décès
  • CMAJ JOURNALS
    • CMAJ Open
    • CJS
    • JAMC
    • JPN

User menu

Search

  • Advanced search
CMAJ
  • CMAJ JOURNALS
    • CMAJ Open
    • CJS
    • JAMC
    • JPN
CMAJ

Advanced Search

  • Home
  • Content
    • Current issue
    • Past issues
    • Early releases
    • Collections
    • Sections
    • Blog
    • Infographics & illustrations
    • Podcasts
    • COVID-19 articles
    • Obituary notices
  • Authors & Reviewers
    • Overview for authors
    • Submission guidelines
    • Submit a manuscript
    • Forms
    • Editorial process
    • Editorial policies
    • Peer review process
    • Publication fees
    • Reprint requests
    • Open access
    • Patient engagement
  • Physicians & Subscribers
    • Benefits for Canadian physicians
    • CPD Credits for CMA Members
    • Subscribe to CMAJ digital
    • Subscribe to CMAJ print
    • Subscription prices
    • Obituary notices
  • Alerts
    • Email alerts
    • RSS
  • JAMC
    • À propos
    • Numéro en cours
    • Archives
    • Sections
    • Abonnement
    • Alertes
    • Trousse média 2023
    • Avis de décès
  • Visit CMAJ on Facebook
  • Follow CMAJ on Twitter
  • Follow CMAJ on Instagram
  • Listen to CMAJ podcasts
Letters

The best protection

John H. Lange
CMAJ June 10, 2003 168 (12) 1524;
John H. Lange
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Responses
  • Metrics
  • PDF
Loading

The transmission of the virus causing severe acute respiratory syndrome (SARS) appears to be by aerosol droplet and possibly through other routes.1 Therefore, it is recommended that health care workers and others who may be exposed1 employ respiratory and other personal protective equipment.2,3 The type of respirator that has typically been used by health care workers is the N95 half-mask.2,3 As correctly stated by Richard Schabas,2 the “N95-rated mask” is 95% filtration efficient,4 but does this level of efficiency provide the best protection for those at risk of exposure? The effectiveness of the N95 respirator has been supported by a small study on prevention of occupational transmission of infection.1 However, for work with bacterial bioaerosols and chemical and biological warfare agents, some have suggested that N95 masks are inappropriate5,6 because these respirators do not provide “absorbent capability” and because of the amount of mask leakage, which can be about 5% through the filter and 10% around the mask,7 even if properly fitted. For biological diseases like SARS, for which just a few particles may be sufficient for infection, the N95 mask may indeed be inadequate, and some health care workers may therefore become infected even if they use the respirator properly.

A better selection for respiratory protection would be an N100 respirator with an ultra-low penetrating air filter (ULPA), which would cost only slightly more than an N95 respirator. N100 respirators have an efficiency of 99.977%,8 and ULPA filters are 99.999% efficient for monodispersed particles 0.12 μm in diameter or larger.9 HEPA (high-efficiency particulate air) filters would not be the best selection for use with a respirator because their efficiency is 99.97% for monodispersed particles 0.3 μm in diameter or larger, and coronaviruses are smaller than this (at about 60 to 200 nm). For effective operation of an N100 respirator with ULPA, the user must be fit-tested. The United States and many other countries have numerous requirements for using a negative-pressure air-purifying respirator, including medical evaluation and training, as well as yearly fit-testing.

John H. Lange Environmental and Occupational Health Consultant Envirosafe Training and Consultants, Inc. Pittsburgh, Pa.

References

  1. 1.↵
    Seto WH, Tsang D, Yung RWH, Ching TY, Ng TK, Ho M, et al. Effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (SARS). Lancet 2003;361:1519-20.
    OpenUrlCrossRefPubMed
  2. 2.↵
    Schabas R SARS: prudence, not panic [editorial]. CMAJ 2003;168:1232-33.
    OpenUrlFREE Full Text
  3. 3.↵
    Centers for Disease Control. Update: severe acute respiratory syndrome – United States, 2003. MMWR Morbid Mortal Wkly Rep 2003;52: 357-60.
    OpenUrlPubMed
  4. 4.↵
    Martyny J, Glazer CS, Newman LS. Respiratory protection. N Engl J Med2002;347:824-30.
    OpenUrlCrossRefPubMed
  5. 5.↵
    Sawicki J. Protection from chemical and biological warfare. Surg Serv Manage 1999;5(Sep):11. Available: www.nbcprotection.com/new/geometarticles/protfromchembiowarfare.htm (accessed 2003 May 14).
  6. 6.↵
    Wake D, Bowry AC, Crook B, Brown RC. Performance of respirator filters and surgical masks against bacterial aerosols. J Aerosol Sci 1997;28: 1311-29.
    OpenUrl
  7. 7.↵
    Occupational Safety and Health Administration. Respiratory protective devices, part II. Final rule. US Federal Register 1995;60:30335-98.
    OpenUrl
  8. 8.↵
    Colton CE, Nelson TJ. Respiratory protection. In: DiNardi SR, editor. The occupational environment — its evaluation and control. Fairfax (VA): American Industrial Hygiene Association; 1997. p. 971-1000.
  9. 9.↵
    ULPA filter. In: Glossary. 1.0 Cleanroom terminology. San Carlos (CA): Servicor; [date unknown]. Available: www.servicor.com/glossary.html (accessed 2003 May 16).
PreviousNext
Back to top

In this issue

CMAJ
Vol. 168, Issue 12
10 Jun 2003
  • Table of Contents
  • Index by author

Article tools

Respond to this article
Print
Download PDF
Article Alerts
To sign up for email alerts or to access your current email alerts, enter your email address below:
Email Article

Thank you for your interest in spreading the word on CMAJ.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
The best protection
(Your Name) has sent you a message from CMAJ
(Your Name) thought you would like to see the CMAJ web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
The best protection
John H. Lange
CMAJ Jun 2003, 168 (12) 1524;

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
‍ Request Permissions
Share
The best protection
John H. Lange
CMAJ Jun 2003, 168 (12) 1524;
Digg logo Reddit logo Twitter logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like

Jump to section

  • Article
    • References
  • Responses
  • Metrics
  • PDF

Related Articles

  • No related articles found.
  • PubMed
  • Google Scholar

Cited By...

  • No citing articles found.
  • Google Scholar

More in this TOC Section

  • A call to reconsider the new diagnostic criteria for gestational diabetes mellitus
  • The 5 Ps need an update: toward a comprehensive sexual history
  • Don’t ignore perimenopause
Show more Letters

Similar Articles

Collections

  • Topics
    • Respiratory medicine

 

View Latest Classified Ads

Content

  • Current issue
  • Past issues
  • Collections
  • Sections
  • Blog
  • Podcasts
  • Alerts
  • RSS
  • Early releases

Information for

  • Advertisers
  • Authors
  • Reviewers
  • CMA Members
  • CPD credits
  • Media
  • Reprint requests
  • Subscribers

About

  • General Information
  • Journal staff
  • Editorial Board
  • Advisory Panels
  • Governance Council
  • Journal Oversight
  • Careers
  • Contact
  • Copyright and Permissions
CMAJ Group

Copyright 2023, CMA Impact Inc. or its licensors. All rights reserved. ISSN 1488-2329 (e) 0820-3946 (p)

All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association or its subsidiaries.

To receive any of these resources in an accessible format, please contact us at CMAJ Group, 500-1410 Blair Towers Place, Ottawa ON, K1J 9B9; p: 1-888-855-2555; e: [email protected]

CMA Civility, Accessibility, Privacy

 

Powered by HighWire