In vivo protective performance of N95 respirator and surgical facemask

Am J Ind Med. 2006 Dec;49(12):1056-65. doi: 10.1002/ajim.20395.


Background: The SARS outbreak in 2003 has spawned a major controversy concerning protective performance facemasks for healthcare workers. This study reports a study on in-vivo protective performance of surgical masks and N95 respirators.

Methods: Typical surgical masks and N95 respirators used in Hong Kong hospitals were tested in comparison with those treated with nano-functional materials (called nano-masks) on various physical properties and in-vivo wear filtration efficiency, as well as usability test in hospitals for surgical masks.

Results: Tests on physical properties showed that N95 respirators had significantly lower air permeability and water vapor permeability than surgical masks. The in-vivo filtration tests illustrated that N95 respirators filtered out 97% of potassium chloride (KCl) solution, while surgical masks filtered out 95% of KCl solution. Nano-masks show stronger water repellency and antibacterial activities, but no difference in usability, comparing with normal N95 and surgical masks.

Conclusions: Surgical masks can provide in-vivo filtration protection of 95% filtration efficiency. N95 respirators provide higher in-vivo filtration efficiency of 97% with significant reduction of air permeability and water vapor permeability. Compared to normal surgical masks/respirators, the nano-masks can provide additional protective functions in stopping capillary diffusion and antibacterial activities.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerosols / chemistry
  • Air Pollutants, Occupational / chemistry*
  • Filtration / instrumentation
  • Health Personnel
  • Humans
  • Infection Control / instrumentation
  • Influenza, Human / prevention & control
  • Inhalation Exposure / prevention & control*
  • Masks / microbiology*
  • Masks / standards
  • Nanoparticles*
  • Occupational Exposure / prevention & control*
  • Particle Size
  • Permeability
  • Respiratory Protective Devices / microbiology*
  • Respiratory Protective Devices / standards
  • Severe Acute Respiratory Syndrome / prevention & control


  • Aerosols
  • Air Pollutants, Occupational