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Cited by 75Infection Control and VentilationAerosol Filtration and Electrostatic PrecipitationOccupational Health and Safety in Workplaces

Nanoparticle Penetration through Filter Media and Leakage through Face Seal Interface of N95 Filtering Facepiece Respirators

Samy Rengasamy, Benjamin C. Eimer·2012·The Annals of Occupational Hygiene
DOI 10.1093/annhyg/mer122
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Abstract

National Institute for Occupational Safety and Health recommends the use of particulate respirators for protection against nanoparticles (<100 nm size). Protection afforded by a filtering facepiece particulate respirator is a function of the filter efficiency and the leakage through the face-to-facepiece seal. The combination of particle penetration through filter media and particle leakage through face seal and any component interfaces is considered as total inward leakage (TIL). Although the mechanisms and extent of nanoparticle penetration through filter media have been well documented, information concerning nanoparticle leakage through face seal is lacking. A previous study in our laboratory measured filter penetration and TIL for specific size particles. The results showed higher filter penetration and TIL for 50 nm size particles, i.e. the most penetrating particle size (MPPS) than for 8 and 400 nm size particles. To better understand the significance of particle penetration through filter media and through face seal leakage, this study was expanded to measure filter penetration at sealed condition and TIL with artificially introduced leaks for 20-800 nm particles at 8-40 l minute volumes for four N95 models of filtering facepiece respirators (FFRs) using a breathing manikin. Results showed that the MPPS was ~45 nm for all four respirator models. Filter penetration for 45 nm size particles was significantly (P < 0.05) higher than the values for 400 nm size particles. A consistent increase in filter penetrations for 45 and 400 nm size particles was obtained with increasing breathing minute volumes. Artificial leakage of test aerosols (mode size ~75 nm) through increasing size holes near the sealing area of FFRs showed higher TIL values for 45 nm size particles at different minute volumes, indicating that the induced leakage allows the test aerosols, regardless of particle size, inside the FFR, while filter penetration determines the TIL for different size particles. TIL values obtained for 45 nm size particles were significantly (P < 0.05) higher than the values obtained for 400 nm size particles for all four models. Models with relatively small filter penetration values showed lower TIL values than the models with higher filter penetrations at smaller leak sizes indicating the dependence of TIL values on filter penetration. When the electrostatic charge was removed, the FFRs showed a shift in the MPPS to ~150 nm with the same test aerosols (mode size ~75 nm) at different hole sizes and breathing minute volumes, confirming the interaction between filter penetration and face seal leakage processes. The shift in the MPPS from 45 to 150 nm for the charge removed filters indicates that mechanical filters may perform better against nanoparticles than electrostatic filters rated for the same filter efficiency. The results suggest that among the different size particles that enter inside the N95 respirators, relatively high concentration of the MPPS particles in the breathing zone of respirators can be expected in workplaces with high concentration of nanoparticles. Overall, the data obtained in the study suggest that good fitting respirators with lower filter penetration values would provide better protection against nanoparticles.

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Crossref · 10.1093/annhyg/mer122

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  • Models N1, N2 and SM1 showed higher TIL values for 45 nm particles than for 300 nm size particles at smaller leak sizes.

    “Models N1, N2 and SM1 showed higher TIL values for 45 nm particles than for 300 nm size particles at smaller leak sizes as reported previously. (24)”

    From A Quantitative Assessment of the Total Inward Leakage of NaCl Aerosol Representing Submicron-Size Bioaerosol Through N95 Filtering Facepiece Respirators and Surgical Masks (2014) · cites this paper as [24]

    The Results section (page unavailable) reports higher TIL for 45 nm than 400 nm particles at many flow rates and leak sizes, supporting the general comparison. But this paper tests models N95-A through N95-D, not N1, N2 and SM1, and uses 400 nm rather than 300 nm as the comparison size. It therefore does not establish the stated result for those specific models and particle sizes. (LLM, conf=0.88)

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  • Because of higher filter efficiency, N95 FFRs are expected to show lower TIL values than SMs.

    “Because of the higher filter efficiency, N95 FFRs are expected to show lower TIL values than do SMs as described previously. (24,26)”

    From A Quantitative Assessment of the Total Inward Leakage of NaCl Aerosol Representing Submicron-Size Bioaerosol Through N95 Filtering Facepiece Respirators and Surgical Masks (2014) · cites this paper as [24]

    The Discussion reports that N95 models with lower filter penetration generally had lower TIL, supporting the proposed relationship between filter efficiency and leakage. But the study compared N95 models, not N95 FFRs with surgical masks (SMs), so it does not establish the claimed comparison; it also notes that larger face-seal leaks can increase TIL despite low filter penetration. Page numbers were not available in our copy. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • All available data have different methodologies and consequently result in different filtering mechanisms.

    “However, all available data have different methodologies and, consequently, result in different filtering mechanisms [15-17].”

    From Bacteria Filtration Efficiency for Different Types of Protective Face Masks (2023) · cites this paper as [15]

    The Discussion distinguishes electrostatic from mechanical filters and describes different particle-capture forces. It does not say that all available data use different methodologies or that methodological differences cause different filtering mechanisms; the distinction it describes concerns filter properties. (LLM, conf=0.78)

    Experimental — accuracy not yet measured

  • The effect of gaps between the face and the mask as caused by an improper fit will affect the efficiency of any face mask for any microorganism.

    “The effect of gaps between the face and the mask as caused by an improper fit will affect the efficiency of any face mask for any microorganism.”

    From Bacteria Filtration Efficiency for Different Types of Protective Face Masks (2023) · cites this paper as [15]

    The Introduction and Discussion (page unavailable) say that face-seal leakage reduces respiratory protection and that better-fitting respirators protect better against nanoparticles. The paper studies N95 respirators and particle leakage; it does not establish the claim for every face mask or every microorganism. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Results obtained in the present study are consistent with the data for four different N95 FFR models tested previously.

    “Results obtained in the present study are consistent with the data for four different N95 FFR models tested previously. (24)”

    From A Quantitative Assessment of the Total Inward Leakage of NaCl Aerosol Representing Submicron-Size Bioaerosol Through N95 Filtering Facepiece Respirators and Surgical Masks (2014) · cites this paper as [24]

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Cites

Flagged first, then by citations

1 of the 30 references couldn’t be matched to a known paper.

Research works printed but not linked: 4

  1. Aitken RJ, Creely KS, Tran CL. (2004) Nanoparticles: an occupational hygiene review. Edinburgh, UK: Institute of occupational Medicine.
  2. Haruta H, Honda T, Eninger RM et al. (2008) Experimental and theoretical investigation of the performance of N95 res- pirator filters against ultrafine aerosols. J Int Soc Res Prot; 25: 75-88.
  3. Hinds WC. (1999) Properties, behavior, and measurement of airborne particles. New York, NY: Wiley-Interscience Publication;
  4. Janssen LL, Weber R. (2005) Effect of pressure drop on respi- rator face seal leakage. J Occup Environ Hyg; 2: 335-40.

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Authors
Rengasamy, S., & Eimer, B. C.
Affiliations
National Institute for Occupational Safety and Health (US)
Corresponding author
Samy Rengasamy
Venue
The Annals of Occupational Hygiene
Publisher
Oxford University Press (OUP)
Published
2012-06-15
Volume
56
Issue
5
Pages
568-80
ISSN
  • 0003-4878 (ISSN-L)
  • 1475-3162
DOI
10.1093/annhyg/mer122
OpenAlex
W2099407296
Cited by
75
References
30
Citations by year
2026: 2 · 2025: 2 · 2024: 5 · 2023: 5 · 2022: 8 · 2021: 10 · 2020: 7 · 2019: 6 · 2018: 6 · 2017: 5 · 2016: 2 · 2015: 2 · 2014: 3 · 2013: 10 · 2012: 1
FWCI
4.13
Type
journal article
Language
en
Open access
closed
Locations
  • The Annals of Occupational Hygiene (publishedVersion)
  • PubMed (publishedVersion)
  • HighWire Press Open Archive (submittedVersion)
Funders
National Institute for Occupational Safety and Health
Topics
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Infection Control and Ventilation
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Aerosol Filtration and Electrostatic Precipitation
  • Health Sciences › Health Professions › Occupational Therapy › Occupational Health and Safety in Workplaces
Keywords
nanoparticles, N95 respirators, filter penetration, most penetrating particle size, static electricity, particulate respirators, nanoparticle protection
MeSH terms
Aerosols, Air Pollutants, Occupational, Equipment Design, Face, Filtration, Humans, Manikins, Materials Testing, Models, Biological, National Institute for Occupational Safety and Health, U.S., Particle Size, Respiratory Protective Devices, United States, Inhalation Exposure, Nanoparticles, Respiratory Rate

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