Hydration of Hydrophilic Cloth Face Masks Enhances the Filtration of Nanoparticles

Zangmeister, Christopher D.; Radney, James G.; Staymates, Matthew E.; Vicenzi, Edward P.; Weaver, Jamie L.

doi:10.1021/acsanm.0c03319

Cited by 29 publications

(24 citation statements)

References 38 publications

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“… a Face velocity is 6.8 cm s –1 . b See technical disclaimer at end of manuscript. c Uncertainties are shown in parentheses; see discussion in text. d See Supporting Information for thickness measurements for the rayon, HEPA vacuum bag, sterilization wrap, and coffee filter. Measurements for 100% cotton flannel can be found in the Supporting Information of ref . e These samples were found to have a large batch-to-batch variability in FE min and Δ P. See Supporting Information for details on these variations. …”

Section: Resultsmentioning

confidence: 99%

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Filter Inserts Impact Cloth Mask Performance against Nano- to Micro-Sized Particles

et al. 2021

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The United States Centers for Disease Control and Prevention and World Health Organization recognize that wearing cloth face coverings can slow the transmission of respiratory diseases via source control. Adding a partial layer of material with a high filtration efficiency (FE, e.g., polypropylene sheets that meet the HEPA standard) as an insert can potentially provide additional personal protection; however, data on the necessary areal coverage are sparse. The relationship between insert area ratio (IAR) relative to fabric area, FE, differential pressure (ΔP, a surrogate for breathability), and quality factor (QF, a ratio including FE and ΔP) utilizing two fabrics (rayon and 100% cotton lightweight flannel) and three insert materials (HEPA vacuum bag, sterilization wrap and paper coffee filter) was investigated. The effect of inserts on particle flows mimicking human exhalation is semiquantitatively and qualitatively examined using flow visualization techniques. The following was found: (1) The relationship between FE, ΔP, and QF is complex, and a trade-off exists between personal protection from filtration during inhalation and source control from leakage during exhalation; (2) FE and ΔP of the composite covering increase with IAR, and the rate is dependent upon insert type; (3) improvements (decrements) in the QF of the composite assemblage require inserts with a higher (lower) QF than the fabric and larger differences yield greater gains (losses); (4) the increased ΔP from an insert results in increased leakage during exhalation; (5) to minimize leaks, ΔP must be as low as possible; and (6) small relative areas not covered by an insert (i.e., IAR slightly smaller than 1) strongly deteriorate the benefits of an insert similar to small leaks in a covering.

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Section: Resultsmentioning

confidence: 99%

“… d See Supporting Information for thickness measurements for the rayon, HEPA vacuum bag, sterilization wrap, and coffee filter. Measurements for 100% cotton flannel can be found in the Supporting Information of ref . …”

Section: Resultsmentioning

confidence: 99%

Filter Inserts Impact Cloth Mask Performance against Nano- to Micro-Sized Particles

et al. 2021

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“…Virion‐containing droplets exiting the oral cavity also contain salt, mucus, lipids and other non‐volatile components, and after dehydration remain highly hygroscopic. Consequently, when traversing a humid mask during ingress, respiratory aerosol will reacquire moisture and swell [108], thereby increasing the likelihood of their capture. This observation may explain why epidemiological evidence points to greater benefits of generic and surgical masks than expected on the basis of their limited dry particle filtering efficiency [110].…”

Section: Respiratory Aerosol Risk Assessmentmentioning

confidence: 99%

Breathing, speaking, coughing or sneezing: What drives transmission of SARS‐CoV‐2?

2021

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The SARS‐CoV‐2 virus is highly contagious, as demonstrated by numerous well‐documented superspreading events. The infection commonly starts in the upper respiratory tract (URT) but can migrate to the lower respiratory tract (LRT) and other organs, often with severe consequences. Whereas LRT infection can lead to shedding of virus via breath and cough droplets, URT infection enables shedding via abundant speech droplets. Their viral load can be high in carriers with mild or no symptoms, an observation linked to the abundance of SARS‐CoV‐2‐susceptible cells in the oral cavity epithelium. Expelled droplets rapidly lose water through evaporation, with the smaller ones transforming into long‐lived aerosol. Although the largest speech droplets can carry more virions, they are few in number, fall to the ground rapidly and therefore play a relatively minor role in transmission. Of more concern is small speech aerosol, which can descend deep into the LRT and cause severe disease. However, since their total volume is small, the amount of virus they carry is low. Nevertheless, in closed environments with inadequate ventilation, they can accumulate, which elevates the risk of direct LRT infection. Of most concern is the large fraction of speech aerosol that is intermediate‐sized because it remains suspended in air for minutes and can be transported over considerable distances by convective air currents. The abundance of this speech‐generated aerosol, combined with its high viral load in pre‐ and asymptomatic individuals, strongly implicates airborne transmission of SARS‐CoV‐2 through speech as the primary contributor to its rapid spread.

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“…These measurements indicate that H 2 O supplied by breathing through the filter can greatly increase the FE of hydrophilic materials principally through particle growth to a size regime with higher FE. 8 …”

Section: Testing Of Common Materials For Filter Mediamentioning

confidence: 99%

Recent developments in filtration media and respirator technology in response to COVID-19

et al. 2021

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The COVID-19 pandemic triggered a surge in demand for N95 or equivalent respirators that the global supply chain was unable to satisfy. This shortage in critical equipment has inspired research that addresses the immediate problems and has accelerated the development of the next-generation filtration media and respirators. This article provides a brief review of the most recent work with regard to face respirators and filtration media. We discuss filtration efficiency of the widely utilized cloth masks. Next, the sterilization of and reuse of existing N95 respirators to extend the existing stockpile is discussed. To expand near-term supplies, optimization of current manufacturing methods, such as melt-blown processes and electrospinning, has been explored. Future manufacturing methods have been investigated to address long-term supply shortages. Novel materials with antiviral and sterilizable properties with the ability for multiple reuses have been developed and will contribute to the development of the next generation of longer lasting multi-use N95 respirators. Finally, additively manufactured respirators are reviewed, which enable a rapidly deployable source of reusable respirators that can use any filtration fabric. Graphic abstract

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Hydration of Hydrophilic Cloth Face Masks Enhances the Filtration of Nanoparticles

Cited by 29 publications

References 38 publications

Filter Inserts Impact Cloth Mask Performance against Nano- to Micro-Sized Particles

Filter Inserts Impact Cloth Mask Performance against Nano- to Micro-Sized Particles

Breathing, speaking, coughing or sneezing: What drives transmission of SARS‐CoV‐2?

Recent developments in filtration media and respirator technology in response to COVID-19

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