Assessment of Nano and Submicron Particle Penetration Criteria of Collective and Individual Layers of Face Mask Substrate

Date

2023-08

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Abstract

The surgical mask has been a crucial tool in mitigating the spread of respiratory diseases caused by viral and particulate pollutants since its invention. It is widely employed in the medical context to mitigate the transmission of infectious agents. The COVID-19 pandemic has resulted in an increased prevalence of surgical mask usage among the general population as a replacement for high-demand respirators, such as the N95. The efficacy of surgical masks and N95 respirators in mitigating the transmission of SARS-CoV-2 remains a topic of contention within the academic discourse. In less economically developed nations, individuals with limited financial resources are unable to procure respirators; thus, they are solely dependent on surgical masks and cloth face coverings. Despite potential counterarguments, the utilization of facial coverings has been critical in reducing the transmission of COVID-19 and will remain a pivotal component of public health initiatives in the future. Therefore, our first study aimed to evaluate the performance of surgical masks and their respective layers with respect to the size of the viruses and particulate matter. The findings indicate an inverse relationship between particle size and penetration percentage of the three-ply surgical mask within the submicron range. The minimum recorded value is 3.67%. Irrespective of the size of the particles, the layer of the polypropylene spun bond material displayed a mean penetration percentage exceeding 85%. However, the uppermost layer of the spun bond material demonstrated a marginally lower percentage of particle penetration than the lowermost spun bond layer. The melt-blown polypropylene layer exhibited decreased penetration percentages in the submicron particle range, with a minimum value of 5.79% observed at a particle size of 400 nm. The observed phenomenon indicates that there is a positive correlation between particle size and both quality factor and protection factor in the context of the three-ply surgical mask, as the particle size shifts from the nanoscale to the submicron scale. Of the 50 samples of three-ply surgical masks tested, 70% were found to have the most penetrating particulate size of 50-60 nm. For this specific particle size, the mean penetration percentage was determined to be 14.9 (±3.79). The global scarcity of critical personal protective equipment (PPE) was triggered by the COVID-19 pandemic, which caused substantial disruptions in the supply chain. Because of this, the CDC issued a statement recommending that people use common fabrics to make cloth face covers and wear them in public as a form of contamination prevention. These face covers are convenient to wear and can be easily washed and reused multiple times. However, it is important to emphasize that cloth face covers should not be considered substitutes for medical-grade personal protective equipment (PPE). Given this context, our second study aimed to enhance and evaluate the effectiveness of face coverings by incorporating filter inserts. These inserts serve as an additional layer of protection against airborne particles, thereby increasing the filtration efficiency of face covers. We conducted a comparative analysis of the efficacy of 12 distinct mask combinations. Our experimental setup involved the utilization of two and four layers of 100% cotton knit, two layers of 100% cotton woven fabric, and two layers of polypropylene spun bond nonwoven fabric as the supporting layers for the masks. Furthermore, we integrated filter layers comprising activated carbon nonwoven, polypropylene melt-blown nonwoven, and glass fiber nonwoven filters. To assess the efficacy of the masks we used selective nanoparticles (30, 40, 60, and 80 nm) and submicron particles (150, 250, 300, and 400 nm) to mimic the viruses and particulate matter. The percentage of particle penetration through the masks was quantified for all possible combinations in accordance with the ASTM F3501-21 protocol. The experimental results suggest that the incorporation of a polypropylene melt-blown nonwoven filter in a combinatorial mask composed of 100% cotton fabric is highly effective in terms of particle penetration percentage, flow resistance, quality factor, and protection factor for both nano- and submicron particles. Additionally, our research indicates that the bulk density of masks serves as a better indicator of particle penetration (%), in accordance with the Pearson correlation coefficient value (r=-0.63). The results of our study indicate that the utilization of filter inserts has a notable positive impact on the filtration efficacy of diverse mask-supporting structures. The comprehensive results of our study will pave the way for further exploration into enhancing the quality, comfort, and design aspects of surgical masks and face coverings in response to a wide range of contagious respiratory threats.


Embargo status: Restricted until 09/2024. To request the author grant access, click on the PDF link to the left.

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Keywords

surgical mask, face cover with filter inserts, SARS-CoV-2, particulate matter, penetration, breathability, quality factor, protection factor

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