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Experimental Measurement of the Size of Gaps Required to Compromise Fit of an N95 Respirator

Published online by Cambridge University Press:  21 January 2022

Eugenia O’Kelly Open the ORCID record for Eugenia O’Kelly [Opens in a new window] ,
Anmol Arora Open the ORCID record for Anmol Arora [Opens in a new window] ,
Sophia Pirog ,
James Ward  and
P. John Clarkson
Eugenia O’Kelly*
Affiliation:
Department of Engineering, University of Cambridge, Cambridge, UK
Anmol Arora
Affiliation:
School of Clinical Medicine, University of Cambridge, Cambridge, UK
Sophia Pirog
Affiliation:
Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
James Ward
Affiliation:
Department of Engineering, University of Cambridge, Cambridge, UK
P. John Clarkson
Affiliation:
Department of Engineering, University of Cambridge, Cambridge, UK
*
Corresponding author: Eugenia O’Kelly, Email eo339@cam.ac.uk.
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Abstract

Objective:

The effectiveness of filtering facepiece respirators such as N95 respirators is heavily dependent on the fit. However, there have been limited efforts to discover the size of the gaps in the seal required to compromise filtering facepiece respirator performance, with prior studies estimating this size based on in vitro models. In this study, we measure the size of leak necessary to compromise the fit of N95 respirators.

Methods:

Two methods were used to create a gap of specific dimensions. A set of 3D-printed resin spacers and hollow steel rods were used to generate gaps in N95 respirators while worn on 2 participants. Occupational Safety and Health Administration (OSHA) quantitative fit testing methods were used to quantify mask performance with gaps between 0.4 and 2.9-mm diameters.

Results:

Gap size was regressed against fit factor, showing that overall, the minimum gap size to compromise N95 performance was between 1.5 mm2 and 3 mm2.

Conclusions:

These findings suggest the fit of a N95 respirator is compromised by gaps that may be difficult to visually detect. The study also adds to the body of evidence supporting the routine use of quantitative fit testing to ensure that masks are well-fitting.

Keywords

coronavirusCOVID-19face coveringsquantitative testingSARS-CoV-2
Type
Original Research
Information
Disaster Medicine and Public Health Preparedness , Volume 17 , 2023 , e118
Copyright
© The Author(s), 2022. Published by Cambridge University Press on behalf of Society for Disaster Medicine and Public Health, Inc.

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