Aurélie Joubert  This email address is being protected from spambots. You need JavaScript enabled to view it., Ala Bouhanguel, Yves Andrès, Laurence Le Coq 

IMT Atlantique, GEPEA, CNRS UMR 6144, 4 Rue Alfred Kastler, CS 20722, F-44307 Nantes, France


Received: July 28, 2023
Revised: October 27, 2023
Accepted: November 22, 2023

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.


Download Citation: ||https://doi.org/10.4209/aaqr.230180  


Cite this article:

Joubert, A., Bouhanguel, A., Andrès, Y., Le Coq, L. (2024). Influence of Test Protocol on Filtration Efficiency of Medical Face Mask Material. Aerosol Air Qual. Res. 24, 230180. https://doi.org/10.4209/aaqr.230180


HIGHLIGHTS

  • Particle size distribution and charge differs according to aerosol generation method.
  • Mask filtration efficiency depends on particle and fiber charges for particles < 3 µm.
  • Mask efficiency is independent of aerosol nature and fiber charge for particles > 3 µm.
  • Mask spectral efficiencies in aerodynamic diameter for MS2 virus and NaCl are matched.
 

ABSTRACT


Medical face masks are an efficient protective barrier against the propagation of bacteria and viruses in societies. The current European standard focuses on the bacterial filtration efficiency of the filtering material for a mean particle size of 3.0 µm in terms of droplets that are exhaled, but viruses that are inhaled can be transported by particles of sub-micron size. The filtration efficiency of medical face mask material was evaluated in a bench test from both unused charged and discharged masks. Several polydisperse test aerosols were used - DEHS, alumina, HOLI, NaCl, Staphylococcus epidermidis and Emesvirus zinderi (MS2) - produced by liquid atomization and/or powder dispersion, and sized by optical and aerodynamic counters or cascade impactors. The results have shown that the particle size distribution and charges for a given type of aerosol can differ depending on the generator used, in particular the wet or dry nature of generation. The results in the sub-micron size range for charged face mask material showed that the filtration efficiency of neutral aerosols was lower than that of charged aerosols due to the electrostatic forces, e.g., 92% versus 99% efficiency for DEHS and alumina respectively for a mean aerodynamic diameter of 0.6 µm. With the discharged face mask material, the filtration efficiency was degraded in the sub-micron size range for all types of aerosol tested: e.g., 30% versus 65% efficiency for a mean optical diameter of 0.25 µm respectively for DEHS and alumina. For particle sizes > 3 µm, the results indicated that the nature of the aerosol has little influence because particle collection is dominated by impaction and interception mechanisms. The tests with MS2 virus demonstrated a good fit with NaCl filtration efficiency expressed in aerodynamic diameters over a range between 0.65 and > 7 µm, for charged and discharged medical face mask materials.


Keywords: Test aerosols, MS2 virus, Electrostatic charges, Particle collection mechanisms




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