title: Respiratory performance offered by N95 respirators and surgical masks: human subject evaluation with NaCl aerosol representing bacterial and viral particle size range.
abstract: OBJECTIVE
  This study aimed at determining the protection factors (PFs) provided by N95 filtering facepiece respirators and surgical masks against particles representing bacterial and viral size ranges (aerodynamic size: 0.04-1.3 mum).
  
  
  METHODS
  The protection levels of N95 filtering facepiece respirators (four models) and surgical masks (three models) were investigated while they were donned by 12 subjects performing the OSHA (US Occupational Safety and Health Administration) fit-testing exercises in a test chamber.
  
  
  RESULTS
  About 29% of N95 respirators and approximately 100% of surgical masks had PFs <10, which is the assigned PF designated for this type of respirator by the OSHA. On average, the PFs of N95 respirators were 8-12 times greater than those of surgical masks. The minimum PFs were observed in the size range of 0.04-0.2 mum. No significant difference in PF results was found between N95 respirators with and without an exhalation valve.
  
  
  CONCLUSIONS
  The study indicates that N95 filtering facepiece respirators may not achieve the expected protection level against bacteria and viruses. An exhalation valve on the N95 respirator does not affect the respiratory protection; it appears to be an appropriate alternative to reduce the breathing resistance.
authors.affiliation: Department of Environmental Engineering and Science, Feng Chia University, Taichung, Taiwan, Republic of China.
authors.forename: Shu-An
authors.initials: SA
authors.lastname: Lee
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Grinshpun
authors.forename: Tiina
authors.initials: T
authors.lastname: Reponen
mesh_terms: D001424:Bacterial Infections / Q000517:prevention & control*; D004867:Equipment Design; D006801:Humans; D018445:Infectious Disease Transmission, Vertical / Q000517:prevention & control; D008397:Masks / Q000592:standards*; D008422:Materials Testing / Q000379:methods; D016273:Occupational Exposure / Q000517:prevention & control; D010316:Particle Size; D012134:Respiratory Protective Devices / Q000592:standards*; D014777:Virus Diseases / Q000517:prevention & control*