Addressing COVID-19 Spread: Development of Reliable Testing System for Mask Reuse

Abstract

While the novel coronavirus pandemic (COVID-19) continues to wreak havoc globally, self-protection from possible infection by wearing a mask in daily life has become the norm in many places. The unprecedented demand for masks has now attracted attention on their filtration efficiency. Furthermore, the widespread use of disposable masks has led to shortage of filter materials and problems with their haphazard disposal. In this study, a testing system that is based on standardized methods has been established and enhanced to reliably measure the particle filtration efficiency (PFE) of masks. Quality control experiments that examine the filtration efficiency of polystyrene latex (PSL) particles that are 0.1 µm in size and sodium chloride (NaCl) particles that range from 0.01-1.0 µm are conducted to determine the reliability of the testing system. Moreover, various textile materials are tested to fabricate 3-layer face masks, and the PFE of these masks is tested by using the proposed testing system to find the most suitable materials and the likelihood of their reusability. Among the tested materials, polytetrafluoroethylene (PTFE) used as the membrane in the filter layer has the highest PFE of 88.33% ± 1.80%, which is mainly due to its dense and multilayer structure. The air permeability of the self-developed masks ranges from 1.41 ± 0.04 to 1.93 ± 0.08, less breathable than the commercial masks. The reusability of a mask that uses PTFE as the membrane in the filter layer is tested by gently washing the mask 30 times and then drying the mask in air before the PFE is measured. The PFE is only reduced by 10-20% after 30 washes, thus indicating the potential reusability of the mask. The findings in this study will contribute to reducing the pressure of mask shortages and are an environmentally friendly solution to the massive use of disposable masks.

Navigating Performance Standards for Face Mask Materials: A Custom‐Built Apparatus for Measuring Particle Filtration Efficiency

“…[ 19 ] Using the same size latex spheres, Lu et al's surgical mask produced average PFE results of 80.2%. [ 20 ] In comparison, our L2 masks performed at a PFE of 94.2 ± 0.6%, and the L3 masks performed at a PFE of 94.9 ± 0.3%. While these PFEs exceed many of those in the literature, we must note that there is little reference to the certification level in the previous studies, whereas our surgical masks were certified at Level 2 and Level 3.…”

“…For example, Bagheri et al (2021), Shakya et al (2016), and Lu et al (2020) constructed apparatuses that generate a polystyrene latex aerosol which was diluted and sent to the material sample, where particle concentration measurements were performed using various particle analyzers or scanning mobility particle sizers. [ 18 , 19 , 20 ] Whereas Lu et al utilized a charge neutralizer downstream of their aerosol generator, the authors of the other two studies did not. Air flow rates at the sample also varied slightly—but within the constraints of the F2299 standard—from ≈7.3 to 19 L min –1 .…”

“…The air face velocities were 2 and 10 cm s –1 (within the standard's range) for the studies by Bagheri et al and Lu et al, respectively, while Shakya et al did not clearly state their face velocity. [ 18 , 19 , 20 ] Furthermore, the authors tested various sizes of latex spheres (i.e., overall, 20 nm up to 2500 nm) with both Shakya et al and Lu et al using the prescribed 100 nm (0.1 µm) particle size in at least some of their tests.…”

Non-Woven Materials for Cloth-Based Face Mask Inserts: Relationship Between Material Properties and Sub-Micron Aerosol Filtration

“…Nevertheless, with two layers of woven fabrics, the PFE ranged from 12.6 % for woven cotton to 30.5 % for flannel, outlining the ineffectiveness of clothbased face coverings against sub-micron aerosols. 37,38 Thus, it is desirable to include a more effective filtration material in layers, particularly for use in the moderate to heavy flow regime expected under moderate physical exertion. 43…”

“…32,36 Several works have shown that cloth-only layers do not provide adequate blocking of submicron aerosols. 37,38 Accordingly, the WHO and other public health agencies are recommending a 3-layer combination comprising a middle non-woven material. To this extent, some studies examined vacuum bag 32 and furnace filters, such as HEPA and MERV-13.…”