Effect of fit testing on the protection offered by n95 filtering facepiece respirators against fine particles in a laboratory setting

Ann Occup Hyg. 2011 Apr;55(3):264-71. doi: 10.1093/annhyg/meq085. Epub 2010 Dec 20.


Objectives: This study investigated particle-size-selective protection factors (PFs) of four models of N95 filtering facepiece respirators (FFRs) that passed and failed fit testing. Particle size ranges were representative of individual viruses and bacteria (aerodynamic diameter d(a) = 0.04-1.3 μm).

Methods: Standard respirator fit testing was followed by particle-size-selective measurement of PFs while subjects wore N95 FFRs in a test chamber. PF values obtained for all subjects were then compared to those obtained for the subjects who passed the fit testing.

Results: Overall fit test passing rate for all four models of FFRs was 67%. Of these, 29% had PFs <10 (the Occupational Safety and Health Administration Assigned Protection Factor designated for this type of respirator). When only subjects that passed fit testing were included, PFs improved with 9% having values <10. On average, the PFs were 1.4 times (29.5/21.5) higher when only data for those who passed fit testing were included. The minimum PFs were consistently observed in the particle size range of 0.08-0.2 μm.

Conclusions: Overall PFs increased when subjects passed fit testing. The results support the value of fit testing but also show for the first time that PFs are dependent on particle size regardless of fit testing status.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aerosols / analysis
  • Analysis of Variance
  • Filtration / instrumentation
  • Filtration / standards
  • Humans
  • Masks / standards*
  • Nanoparticles
  • Occupational Exposure / prevention & control
  • Particle Size*
  • Respiratory Protective Devices / standards*


  • Aerosols