scholarly journals The protective performance of reusable cloth face masks, disposable procedure masks, KN95 masks and N95 respirators: Filtration and total inward leakage

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258191
Author(s):  
Scott Duncan ◽  
Paul Bodurtha ◽  
Syed Naqvi
Keyword(s):  
Geometric Mean ◽  
Particle Diameter ◽  
Standing Position ◽  
Filtration Efficiency ◽  
Protection Factor ◽  
Respiratory Illnesses ◽  
Particle Penetration ◽  
Preventive Health Measure ◽  
Materials Used ◽  
N95 Respirators

Face coverings are a key component of preventive health measure strategies to mitigate the spread of respiratory illnesses. In this study five groups of masks were investigated that are of particular relevance to the SARS-CoV-2 pandemic: re-usable, fabric two-layer and multi-layer masks, disposable procedure/surgical masks, KN95 and N95 filtering facepiece respirators. Experimental work focussed on the particle penetration through mask materials as a function of particle diameter, and the total inward leakage protection performance of the mask system. Geometric mean fabric protection factors varied from 1.78 to 144.5 for the fabric two-layer and KN95 materials, corresponding to overall filtration efficiencies of 43.8% and 99.3% using a flow rate of 17 L/min, equivalent to a breathing expiration rate for a person in a sedentary or standing position conversing with another individual. Geometric mean total inward leakage protection factors for the 2-layer, multi-layer and procedure masks were <2.3, while 6.2 was achieved for the KN95 masks. The highest values were measured for the N95 group at 165.7. Mask performance is dominated by face seal leakage. Despite the additional filtering layers added to cloth masks, and the higher filtration efficiency of the materials used in disposable procedure and KN95 masks, the total inward leakage protection factor was only marginally improved. N95 FFRs were the only mask group investigated that provided not only high filtration efficiency but high total inward leakage protection, and remain the best option to protect individuals from exposure to aerosol in high risk settings. The Mask Quality Factor and total inward leakage performance are very useful to determine the best options for masking. However, it is highly recommended that testing is undertaken on prospective products, or guidance is sought from impartial authorities, to confirm they meet any implied standards.

scholarly journals N95 respirators, disposable procedure masks and reusable cloth face coverings: total inward leakage and filtration efficiency of materials against aerosol

2020 ◽  
Author(s):  
Scott Duncan ◽  
Paul Bodurtha ◽  
Syed Naqvi
Keyword(s):  
Filtration Efficiency ◽  
Protection Factor ◽  
Protection Level ◽  
Aerosol Emission ◽  
Mask Material ◽  
Preventive Health Measure ◽  
The Face ◽  
Materials Used ◽  
N95 Respirators ◽  
Penetration Tests

AbstractHumans expel physiological particles continuously through normal respiratory activities such as breathing, talking, coughing and sneezing; a portion of these are aerosol in the size range <5.0 µm. Misconceptions exist on how to best implement face coverings as an effective preventive health measure against potentially infectious respiratory generated aerosol. The aim of this study was to characterise the performance of face coverings against aerosol when worn by individuals, and to quantify the maximum aerosol penetration through the material used in the construction of each mask. The former addresses their use as a means of possible protection against aerosol present in the environment and the latter having relevance to filtration and reducing human generated aerosol from reaching the environment. Face covering performance was assessed by measuring the total inward leakage of aerosol through the mask material and face seal. Aerosol penetration was measured on swatches of material taken from the face covering. An inert polydisperse charge-neutralized NaCl aerosol, with a distribution ranging from 0.023 µm to 5 μm in diameter, was used for the experiments.Total inward leakage tests were completed to assess the protection factor for nine variations of face coverings, including seven reusable cloth masks, of which six were homemade and one was commercially manufactured, and two styles of disposable procedure masks, one with ear loops and one with ties. Our results have shown that face coverings in general provide the wearer only limited protection against aerosol in the environment. All reusable cloth face coverings obtained a practical protection level of less than 2. The performance of the disposable procedure masks varied from 1.7 to 3.6. The mean practical protection level for the nine face coverings was 1.95 with a standard deviation of 0.89. Comparatively, a N95 respirator achieved a protection factor of 166. We have further shown that aerosol readily penetrates through most materials used in face coverings. Aerosol swatch penetration tests were completed on six different fabrics commonly available for reusable homemade face coverings, four different material systems comprised of multiple material types, eight different disposable procedure masks and the filtering material from three different N95 respirators. Maximum aerosol penetration through the six common fabrics varied from 39% to 91%; for systems comprised of multiple types of materials 4% to 23%; for materials used in disposable procedure masks 16% to 80%; and for filtering materials used in N95 respirators 1.0% to 1.9%. We also highlight that with the exception of some of the reusable cloth materials, penetration of particulates at 5 µm diameter, representing the minimum filtration efficiency that could be achieved against droplets, was insignificant; the six common fabrics showed penetration from 1% to 44%; the fabric systems comprised of multiple types of materials <0.9%; the materials used in disposable procedure masks <0.9% to 6%; and the filtering materials used in three different N95 respirators <0.9%. The observations from this study directly demonstrate that face coverings may be optimized by incorporating high filtration efficiency materials in their construction. Face coverings with an enhanced level of filtration would be of benefit in circumstances where SARS-CoV-2 may be present in the aerosol of infected individuals to reduce aerosol emission from respiratory activities penetrating through into the environment.

scholarly journals Quantifying Mask Leakage and Effectiveness for Public Health Messaging

2021 ◽  
Author(s):  
Charles Freeman ◽  
Reuben Burch ◽  
Lesley Strawderman ◽  
Catherine Black ◽  
David Saucier ◽  
...  
Keyword(s):  
Public Health ◽  
Filtration Efficiency ◽  
Differential Pressure ◽  
Respiratory Illnesses ◽  
N95 Respirators ◽  
Significant Factors ◽  
Health Messaging

Abstract The purpose of this study is to compare masks (non-medical/fabric, surgical, and N95 respirators) on filtration efficiency, differential pressure, and leakage with the goal of providing evidence to improve public health messaging. Masks were tested on an anthropometric face filtration mount comparing both sealed and unsealed. Overall, surgical and N95 respirators provided significantly higher for filtration efficiency and differential pressure. Leakage comparisons are one of the most significant factors in mask efficiency. Higher weight and thicker fabric masks had significantly higher filtration efficiency. The findings of this study have important implications for communication and education regarding the use of masks to prevent the spread of COVID-19 and other respiratory illnesses specifically the differences between sealed and unsealed masks. One-Sentence Summary: The type and fabric of facial masks and whether a mask is sealed or unsealed has a significant impact on the effectiveness of a mask.

scholarly journals Study on filtration performance of elliptical fiber with different arrangements

2020 ◽  
Vol 15 ◽  
pp. 155892501989388
Author(s):  
JiaWei Zhou ◽  
Liang Zhang ◽  
Bo Zhang ◽  
Wei Gong
Keyword(s):  
Quality Factor ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Particle Diameter ◽  
Dense Layer ◽  
Fibrous Media ◽  
Bimodal Structure ◽  
Filtration Performance ◽  
Particle Penetration ◽  
Circular Fiber

The fibrous media composed of elliptical fibers is widely used owing to the high filtration efficiency. However, there are few studies on the arrangement of non-circular fibers, although the single non-circular fiber has been clearly investigated. In this article, two-dimensional numerical geometries of fibrous media with different elliptical fiber arrangements, namely, random distribution structure, dense–sparse structure, and bimodal structure, are developed for studying filtration performance. The results show that the large aspect ratio and solid volume fraction represent low particle penetration. When the particle diameter ( Dp) is small, the quality factor of bimodal structure is higher than the dense–sparse structure, especially at Dp = 50 nm. For the large Dp, the opposite is true. Meanwhile, reducing fiber diameter ( Df) is more significant than increasing solid volume fraction in terms of improving penetration. As for dense–sparse structure, replacing the elliptical fibers in sparse layers with circular fibers can comprehensively improve the quality factor of fibrous media. However, if the replacement between elliptical fiber and circular fiber occurs in dense layer, it will result in high quality factor at Dp ⩽ 500 nm, while low quality factor at Dp > 500 nm.

scholarly journals Scalable In-hospital Decontamination of N95 Filtering Facepiece Respirator with a Peracetic Acid Room Disinfection System

2020 ◽  
Author(s):  
Amrita R. John ◽  
Shine Raju ◽  
Jennifer L. Cadnum ◽  
Kipum Lee ◽  
Phillip McClellan ◽  
...  
Keyword(s):  
Peracetic Acid ◽  
Structural Integrity ◽  
Filtration Efficiency ◽  
Material Structure ◽  
Cycle Duration ◽  
Bacteriophage Ms2 ◽  
Large Numbers ◽  
Care Workers ◽  
High Level ◽  
N95 Respirators

AbstractBackgroundCritical shortages of personal protective equipment (PPE) especially N95 respirators, during the SARS-CoV-2 pandemic continues to be a source of great concern among health care workers (HCWs). Novel methods of N95 filtering facepiece respirator (FFR) decontamination that can be scaled-up for in-hospital use can help address this concern and keep HCWs safe.MethodsA multidisciplinary pragmatic study was conducted to evaluate the use of an ultrasonic room high-level disinfection system (HLDS) that generates aerosolized peracetic acid (PAA) and hydrogen peroxide for decontamination of large numbers of N95 respirators. A cycle duration that consistently achieved disinfection of N95 respirators (defined as ≤ 6 log10 reductions in bacteriophage MS2 and Geobacillus stearothermophilus spores inoculated onto respirators) was identified. The treated masks were then assessed for changes to their hydrophobicity, material structure, strap elasticity, and filtration efficiency (FE). Assessment of PAA off-gassing from a treated mask was also performed.ResultsThe PAA room HLDS was effective for disinfection of N95 respirators in a 2447 cubic feet room with deploy and dwell times of 16 and 32 minutes respectively, and a total cycle time of 1 hour and 16 minutes. After 5 treatment cycles, no adverse effects were detected on filtration efficiency, structural integrity, or strap elasticity. There was no detectable off-gassing of PAA from the treated masks.ConclusionThe PAA room disinfection system provides a rapidly scalable solution for in-hospital decontamination of large numbers of N95 respirators to meet the needs of HCWs during the SARS-CoV-2 pandemic.

scholarly journals Ethanol-Drying Regeneration of N95 Respirators

2020 ◽  
Author(s):  
Albert I. Nazeeri ◽  
Isaac A. Hilburn ◽  
Daw-An Wu ◽  
Kabir A. Mohammed ◽  
D. Yovan Badal ◽  
...  
Keyword(s):  
Standardized Testing ◽  
Rural Areas ◽  
Degradation Mechanism ◽  
Adsorbed Water ◽  
Filtration Efficiency ◽  
Drying Methods ◽  
Routine Practice ◽  
Filter Efficiency ◽  
Filtering Efficiency ◽  
N95 Respirators

AbstractA critical shortage of respirators, masks and other personal protective equipment (PPE) exists due to the COVID-19 pandemic. Of particular need are N95 respirators, which use meltblown microfibers of charged polypropylene. An intensive search is underway to find reliable methods to lengthen the useful life of these normally disposable units.Recent experiments on respirators cleaned with ethanol solutions found drastic post-treatment drops infiltration efficiency (>40%). This has been attributed to a mechanism whereby ethanol disrupts the charges in the microfibers, reducing their ability to trap particles. The CDC/NIOSH has issued guidance directing clinicians and researchers to pursue other methods of decontamination.In our experiments, we replicated the drop in efficiency after 70% ethanol treatment, but we found that the efficiency rose again after more effective drying, which we achieved with a vacuum chamber. After drying at pressures of < ∼6 mbar (0.6 kPa), the measured filtering efficiency rose to within 2% of the pre-washing value, and we found that this was sustained for 5 cleaning-drying cycles in three models of N95 masks. We stress that our tests are not meant to certify that the respirators are safe for use, which would require further, standardized, testing under NIOSH protocols. The tests presented here are used to understand basic mechanisms by which treatments can decrease or increase filtration efficiency.The main mechanism underlying the loss and recovery of filter efficiency seems to be the deposition and removal of water molecules adsorbed on the fiber surfaces, a hypothesis which is supported by several observations: (A) the filtering efficiency increases non-linearly with the weight loss during drying. (B) filtration efficiency shows an abrupt recovery as the vacuum pressure drops from 13 to 6 mbar, the range physically attributable to the removal of adsorbed water. (C) Optical microscopy of the microfiber layer reveals surface wetting of the fibers, which is most resistant to drying in dense regions of the fiber network. These observations indicate that losses in filter efficiency may be caused by the wicking of water into the dense fiber networks, reducing the available surface area for filtration.Such a degradation mechanism has two implications: (A) Ethanol and other aqueous decontamination methods may be more viable than previously assumed. Investigations of such methods should specify drying methods in their protocols. We employ vacuum chambers in this study, but other methods of removing adsorbed water could be equivalent. (B) This mechanism presents the possibility that mask filtration performance may be subject to degradation by other sources of moisture, and that the mask would continue to be compromised even if it appears dry. Further research is needed to determine the conditions under which such risks apply, and whether drying should be a routine practice for respirators undergoing extended use.This study introduces a number of methods which could be developed and validated for use in resource-limited settings. As the pandemic continues to spread in rural areas and developing nations, these would allow for local efforts to decontaminate, restore, and test medical masks.

scholarly journals Estimation of the chemical specific surface area of catalytic nanoparticles by TEM images analysis

2018 ◽  
Vol 1 (87) ◽  
pp. 5-12 ◽  
Author(s):  
M. Pawlyta ◽  
B. Sobel ◽  
B. Liszka
Keyword(s):  
Fuel Cells ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Platinum Nanoparticles ◽  
Quantitative Methods ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Platinum Particles ◽  
Materials Used

Purpose: The purpose of this article is the development of quantitative methods for assessing the quality of nanocomposite materials used in fuel cells. Design/methodology/approach: latinum is the most commonly used catalyst in fuel cells, commonly in the form of nanoparticles deposited on the surface of carbon black. Due to the nanometric size of platinum particles, transmission electron microscopy can be applied to evaluate the produced catalysts. TEM image also allow to determinate the approximate value of the chemical specific surface area) of platinum nanoparticles, but only in case of spherical particles. Findings: In present work, taking into account additional assumptions resulting directly from the analysis of microscopic images, the method of estimation of the particle diameter and the chemical specific surface area for nonsymmetrical (elongated) nanoparticles is present. Research limitations/implications: The presented work presents a method for determining the specific surface of platinum, when their shape is elongated. It is worth noting that the modified formulas for determining the particle diameter and the value of the chemically active specific surface of the platinum nanoparticles of the elongated shape are equivalent to the formulas previously given for spherical particles, if the particle length and its diameter are equal. In this case, patterns for symmetric particles and more general (modified) patterns can be used interchangeably. Practical implications: Development of new and more effective catalysts for fuel cells. Originality/value: The significance of the presented work results from the possibility of using the described method in the catalyst studies during real catalytic processes. It allows comparing catalytic activity after the process, also in unusual conditions and in an aggressive environment, using minimal amounts of material.

scholarly journals Reprocessing N95 Respirators During the COVID-19 Pandemic: Moist Heat Inactivates SARS-CoV-2 and Maintains N95 Filtration

2020 ◽  
Author(s):  
Simeon C. Daeschler ◽  
Niclas Manson ◽  
Kariym Joachim ◽  
Alex W. H. Chin ◽  
Katelyn Chan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Cost ◽  
Filtration Efficiency ◽  
Term Care ◽  
Protective Function ◽  
E Coli ◽  
Breathing Resistance ◽  
N95 Respirators ◽  
Scanning Electron

AbstractBackgroundThe unprecedented demand and consequent global shortage of N95 respirators during the COVID-19 pandemic have left frontline workers vulnerable to infection. To potentially expand the supply, we validated a rapidly applicable low-cost decontamination protocol in compliance with regulatory standards to enable the safe reuse of personalized, disposable N95-respirators.MethodsFour common models of N95-respirators were disinfected for 60 minutes at 70°C either at 0% or 50% relative humidity (RH). Effective inactivation of SARS-CoV-2 and E. coli was evaluated in inoculated masks. The N95 filter integrity was examined with scanning electron microscopy. The protective function of disinfected N95 respirators was tested against US NIOSH standards for particle filtration efficiency, breathing resistance and respirator fit.ResultsA single heat treatment inactivated both SARS-CoV-2 (undetectable, detection limit: 100 TCID50/ml) and E. coli (0 colonies at 50%RH) in all four respirator models. Even N95-respirators that underwent ten decontamination cycles maintained their integrity and met US-governmental criteria for approval regarding fit, filtration efficiency and breathing resistance. Scanning electron microscopy demonstrated maintained N95 fiber diameter compared to baseline.InterpretationThermal disinfection enables large-scale, low cost decontamination of existing N95 respirators using commonly sourced equipment during the COVID-19 pandemic. This process could be used in hospitals and long term care facilities and also provides a feasible approach to expand the N95 supply in low- and middle-income regions.

scholarly journals Determination of Dissolution Rates of Ag Contained in Metallurgical and Mining Residues in the S2O32−-O2-Cu2+ System: Kinetic Analysis

Minerals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 309 ◽  
Author(s):  
Julio Juárez Tapia ◽  
Francisco Patiño Cardona ◽  
Antonio Roca Vallmajor ◽  
Aislinn Teja Ruiz ◽  
Iván Reyes Domínguez ◽  
...  
Keyword(s):  
Kinetic Study ◽  
Dissolution Rate ◽  
Catalytic Effect ◽  
Particle Diameter ◽  
Favorable Effect ◽  
Leaching Rate ◽  
Materials Used ◽  
Mining Residues ◽  
Thiosulfate Concentration

The materials used to conduct kinetic study on the leaching of silver in the S2O32−-O2-Cu2+ system were mining residues (tailings) from the Dos Carlos site in the State of Hidalgo, Mexico, which have an estimated concentration of Ag = 71 g∙ton−1. The kinetic study presented in this paper assessed the effects of the following variables on Ag dissolution rate: particle diameter (d0), temperature (T), copper concentration [Cu2+], thiosulfate concentration [S2O32−], pH, [OH−], stirring rate (RPM), and partial pressure of oxygen (PO2). Temperature has a favorable effect on the leaching rate of Ag, obtaining an activation energy (Ea) = 43.5 kJ∙mol−1 in a range between 288 K (15 °C) and 328 K (55 °C), which indicates that the dissolution reaction is controlled by the chemical reaction. With a reaction order of n = 0.4, the addition of [Cu2+] had a catalytic effect on the leaching rate of silver, as opposed to not adding it. The dissolution rate is dependent on [S2O32−] in a range between 0.02 mol·L−1 and 0.06 mol·L−1. Under the studied conditions, variables d0, [OH−] and RPM did not have an effect on the overall rate of silver leaching.

A Study on Fluidized Bed-Type Particulate Filter for Diesel Engines

2007 ◽  
Vol 129 (4) ◽  
pp. 1072-1078 ◽  
Author(s):  
Sung-Sub Kee ◽  
Ali Mohammadi ◽  
Takuji Ishiyama ◽  
Takaaki Kakuta
Keyword(s):  
Particle Size ◽  
Diesel Engine ◽  
Pressure Drop ◽  
Fluidized Bed ◽  
Particle Diameter ◽  
Filtration Efficiency ◽  
Particulate Filter ◽  
Design Parameters ◽  
Gas Velocity ◽  
Bed Height

A fluidized bed-type diesel particulate filter (DPF) was applied to filter particulate matter (PM) in diesel engine exhaust gas. The effects of the fluidized bed design parameters, such as gas velocity, bed particle size, and height, on PM and smoke filtration efficiencies, and pressure drop were experimentally investigated using a single-cylinder direct injection (DI) diesel engine. High PM filtration efficiency and low pressure drop were achieved with the DPF, especially at a lower gas velocity. The PM filtration efficiency was higher with a smaller bed particle size at the lower gas velocity; however, it drastically decreased with an increase in gas velocity due to excessive fluidization of the bed particles. Increase in bed height led to higher PM filtration efficiency while causing an increase in pressure drop. The theoretical work was also conducted for further investigation of the effects of the above-mentioned parameters on PM filtration. These results indicated that diffusion filtration was the dominant mechanism for PM filtration under the conditions of this study and that the decrease in PM filtration efficiency at high gas velocity was caused by a deterioration in the diffusion filtration. The bed particle diameter and the bed height should be optimized in order to obtain a high filtration efficiency without increasing the DPF size.

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