Surgical masks vs P2 (N95) respirators #2

 in Infection Control / Occupational Hygiene / Respiratory protection  tagged Face masks / Myths / Respiratory protection / Swine Flu by

A recent paper MacIntyre, C. R., S. Cauchemez, et al. (2009). “Face Mask Use and Control of Respiratory Virus Transmission in Households.” Emerging Infectious Diseases 15(2): 233-241. is available from the CDC  as free download Unfortunately, despite the warning “We urge caution in extrapolating our results to school, workplace, or community contexts, or where multiple, repeated exposures may occur, such as in healthcare settings. “, the report is being taken in media reports to mean that surgical masks give adequate protection against the Influenza H1N1 swine flu virus.

The paper studied the performance of un-fitted P2 masks and surgical masks for protection in the home against Influenza like diseases in the home found that they gave similar (60-80%) protection, though statistically they could not differentiate the approaches. The masks were only worn about 30% of the time and no information was given on the fitting instructions, despite this being a key piece of information. Interestingly, many of the references are about hand washing, but none (except for a 3M information sheet) were about the fit of respirators.

For the very narrow context of the applicability of the paper, it was well designed. To me, the paper shows the real need for proper fit testing of P2/ N95 respirators to reach their protection potential.

I think most people who were concerned enough about swine flu to wear a face mask would want to get a high level of protection and know how to fit one to give significantly better protection than a surgical mask. Common surgical masks are not designed or certified for respiratory protection.

Some of the papers and reports relating to both N95/P2 respirators and surgical masks are:

  • Balazy, A., M. Toivola, et al. (2006). “Do N95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks?” Am J Infect Control 34(2): 51-7.
  • Brosseau, L. M. and K. Harriman (2007). “In vivo protective performance of N95 respirator and surgical facemask.” American Journal of Industrial Medicine 50(12): 1025-1026.
  • Duling, M. G., R. B. Lawrence, et al. (2007). “Simulated Workplace protection factors for half-facepiece respiratory protective devices.” Journal of Occupational and Environmental Hygiene 4(6): 420-431.
  • Guo, Y. (2007). “Reply to the comments on ldquoin vivo protective performance of N95 respirator and surgical face mask rdquo.” American Journal of Industrial Medicine 50(12): 1027-1029.
  • Jefferson, T., R. Foxlee, et al. (2007). “Interventions for the interruption or reduction of the spread of respiratory viruses.” Cochrane Database of Systematic Reviews(4).
  • Lawrence, R. B., M. G. Duling, et al. (2006). “Comparison of performance of three different types of respiratory protection devices.” Journal of Occupational and Environmental Hygiene 3(9): 465-474.
  • Lee, S. A., S. A. Grinshpun, et al. (2008). “Respiratory performance offered by N95 respirators and surgical masks: human subject evaluation with NaCl aerosol representing bacterial and viral particle size range.” Ann Occup Hyg 52(3): 177-85.
  • Li, Y., T. Wong, et al. (2006). “In vivo protective performance of N95 respirator and surgical facemask.” American Journal of Industrial Medicine 49(12): 1056-1065.
  • Li, Y., T. Wong, et al. (2006). “In vivo protective performance of N95 respirator and surgical facemask.” American Journal of Industrial Medicine 49(12): 1056-1065.
  • PandemicFlu.gov (2007). Interim Public Health Guidance for the Use of Facemasks and Respirators in Non-Occupational Community Settings during an Influenza Pandemic, US Department of Health and Human Services.
  • Qian, Y. G., K. Willeke, et al. (1998). “Performance of N95 respirators: Filtration efficiency for airborne microbial and inert particles.” American Industrial Hygiene Association Journal 59(2): 128-132.
  • Rebmann, T., R. Wilson, et al. (2009). “Hospital infectious disease emergency preparedness: A 2007 survey of infection control professionals.” American Journal of Infection Control 37(1): 1-8.
  • Roberge, R. J. (2008). “Effect of surgical masks worn concurrently over N95 filtering facepiece respirators: extended service life versus increased user burden.” J Public Health Manag Pract 14(2): E19-26.
  • WHO (2005). Clarification – Use of masks by health-care workers in pandemic settings. Geneva.

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