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

Abstract

Objectives: 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 two participants. Occupational Safety and Health Administration (OSHA) quantitative fit testing methods were used to quantify mask performance with gaps between 0.4 and 2.9mm diameters. Results: Gap size was regressed against fit factor, showing that overall the minimum gap size to compromise N95 performance was between 1.5mm2 and 3mm2. 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.

The Influence of Head Strap Elasticity on the Protective Properties of Filtering Facepiece Respirators

“…Many scientific studies have been devoted to the improvement of filtering respirators. In particular, there have been proposed: a rational design of the perforated obturator (Cheberiachko et al, 2023), a production of filter respirator half-masks with a special frame (Cai et al, 2018), reinforcement of the obturator of the filtering respirator in the area of the nose with an additional seal (Kwon et al, 2022), application of sealants between a half mask and a face (Chopra et al, 2021;O'Kelly et al, 2022;Caggiari et al, 2022). Multiple use of respirators has been investigated (Małgorzata et al, 2023).…”

Increasing the Insulation Properties of Filter Respirators to Protect Miners’ Respiratory Organs From Dust

“…In the case of half-masks of a filtering respirator with an airtight facepiece, the reliability of isolation depends on the design of the obturator and the material it is made of. The following seals between the half-mask and the face are known: "single-skin respirator seal" (normal, single fold), "airbag" (inflatable obturator), "reflex" (flexible U-shaped fold providing two contact strips) and "double-bladed respirator seal» (corrugated obturator with two strips touching the face) (Caggiari et al, 2016;Chopra et al, 2021;O'Kelly et al, 2022). The best one is the last one.…”