scholarly journals Performance of Valved Respirators to Reduce Respiratory Particles Generated by Speaking

2021 ◽  
Author(s):  
Jessica M Hazard ◽  
Christopher D Cappa
Keyword(s):  
Material Design ◽  
Filtration Efficiency ◽  
Source Control ◽  
Ambient Particles ◽  
Highly Efficient ◽  
Reliable Source ◽  
N95 Respirators

Wearing of face coverings serves two purposes: reducing the concentration of ambient particles inhaled and reducing the emission of respiratory particles generated by the wearer. The efficiency of different face coverings depends on the material, design, and fit. Face coverings such as N95 respirators, when worn properly, are highly efficient at filtering ambient particles during inhalation. Some N95 respirators, as well as other face covering types, include a one-way valve to allow easier exhalation while still maintaining high filtration efficiency towards ambient particles. The extent to which these valves decrease filtration of emitted respiratory particles is, however, not well established. Here, we show that different valved N95s exhibit highly variable filtration efficiencies for exhaled respiratory particles. As such, valved N95s do not provide reliable source control of respired particles and their use should be discouraged in situations where such source control is needed.

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.

Highly efficient halogen-free solvent processed small-molecule organic solar cells enabled by material design and device engineering

2017 ◽  
Vol 10 (8) ◽  
pp. 1739-1745 ◽  
Author(s):  
Jiahui Wan ◽  
Xiaopeng Xu ◽  
Guangjun Zhang ◽  
Ying Li ◽  
Kui Feng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Energy Loss ◽  
Small Molecules ◽  
Small Molecule ◽  
Organic Solar Cells ◽  
Material Design ◽  
Small Energy ◽  
Highly Efficient ◽  
Device Engineering ◽  
Halogen Free

Naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole-based small molecules have been synthesized for organic solar cells. The optimized devices processed by a halogen-free solvent of CS2 exhibited a PCE of 11.53% with a small energy loss of 0.57 eV.

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 Comprehensive Review of Polysaccharide-Based Materials in Edible Packaging: A Sustainable Approach

Foods ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1845
Author(s):  
Yuan Zhao ◽  
Bo Li ◽  
Cuicui Li ◽  
Yangfan Xu ◽  
Yi Luo ◽  
...  
Keyword(s):  
Food Packaging ◽  
Fruits And Vegetables ◽  
Material Design ◽  
Antimicrobial Activities ◽  
Product Packaging ◽  
Polymers And Plastics ◽  
Film Forming ◽  
Reliable Source ◽  
Petroleum Resources ◽  
Edible Packaging

Edible packaging is a sustainable product and technology that uses one kind of “food” (an edible material) to package another kind of food (a packaged product), and organically integrates food with packaging through ingenious material design. Polysaccharides are a reliable source of edible packaging materials with excellent renewable, biodegradable, and biocompatible properties, as well as antioxidant and antimicrobial activities. Using polysaccharide-based materials effectively reduces the dependence on petroleum resources, decreases the carbon footprint of the “product-packaging” system, and provides a “zero-emission” scheme. To date, they have been commercialized and developed rapidly in the food (e.g., fruits and vegetables, meat, nuts, confectioneries, and delicatessens, etc.) packaging industry. However, compared with petroleum-based polymers and plastics, polysaccharides still have limitations in film-forming, mechanical, barrier, and protective properties. Therefore, they need to be improved by reasonable material modifications (chemical or physical modification). This article comprehensively reviews recent research advances, hot issues, and trends of polysaccharide-based materials in edible packaging. Emphasis is given to fundamental compositions and properties, functional modifications, food-packaging applications, and safety risk assessment of polysaccharides (including cellulose, hemicellulose, starch, chitosan, and polysaccharide gums). Therefore, to provide a reference for the development of modern edible packaging.

scholarly journals Evaluation of Different Types of Face Masks to Limit the Spread of SARS-CoV-2 – A Modeling Study

2021 ◽  
Author(s):  
Brian M. Gurbaxani ◽  
Andrew N. Hill ◽  
Prabasaj Paul ◽  
Pragati V. Prasad ◽  
Rachel B. Slayton
Keyword(s):  
The United States ◽  
Basic Reproductive Number ◽  
Transmission Model ◽  
Source Control ◽  
Reproductive Number ◽  
Medical Procedure ◽  
Different Types ◽  
Protection Efficacy ◽  
N95 Respirators ◽  
Related Mortality

AbstractWe updated a published mathematical model of SARS-CoV-2 transmission with laboratory-derived source and wearer protection efficacy estimates for a variety of face masks to estimate their impact on COVID-19 incidence and related mortality in the United States. When used at already-observed population rates of 80% for those ≥65 years and 60% for those <65 years, face masks are associated with 69% (cloth) to 78% (medical procedure mask) reductions in cumulative COVID-19 infections and 82% (cloth) to 87% (medical procedure mask) reductions in related deaths over a 6-month timeline in the model. If cloth or medical procedure masks’ source control and wearer protection efficacies are boosted about 30% each to 84% and 60% by cloth over medical procedure masking, fitters, or braces, the COVID-19 basic reproductive number of 2.5 could decrease to an effective reproductive number ≤ 1.0, and from 4.0 to ≈ 1.6 for the B.1.1.7 variant.Article Summary LineAdapting a published SARS-CoV-2 transmission model together with updated, laboratory-derived source control and wearer protection efficacy estimates for a variety of face coverings as well as N95 respirators, we demonstrate that community masking as currently practiced has likely reduced cases and deaths and that this benefit can be increased with wider adoption of better performing masks.

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 Gamma radiation sterilization of N95 respirators leads to decreased respirator performance

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0248859
Author(s):  
Haedi E. DeAngelis ◽  
Anne M. Grillet ◽  
Martin B. Nemer ◽  
Maryla A. Wasiolek ◽  
Don J. Hanson ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Electrostatic Potential ◽  
Particle Filtering ◽  
Performance Testing ◽  
Field Measurements ◽  
The United States ◽  
Filtration Efficiency ◽  
Radiation Sterilization ◽  
Potential Measurement ◽  
N95 Respirators

In response to personal protective equipment (PPE) shortages in the United States due to the Coronavirus Disease 2019, two models of N95 respirators were evaluated for reuse after gamma radiation sterilization. Gamma sterilization is attractive for PPE reuse because it can sterilize large quantities of material through hermetically sealed packaging, providing safety and logistic benefits. The Gamma Irradiation Facility at Sandia National Laboratories was used to irradiate N95 filtering facepiece respirators to a sterilization dose of 25 kGy(tissue). Aerosol particle filtration performance testing and electrostatic field measurements were used to determine the efficacy of the respirators after irradiation. Both respirator models exhibited statistically significant decreases in particle filtering efficiencies and electrostatic potential after irradiation. The largest decrease in capture efficiency was 40–50% and peaked near the 200 nm particle size. The key contribution of this effort is correlating the electrostatic potential change of individual filtration layer of the respirator with the decrease filtration efficiency after irradiation. This observation occurred in both variations of N95 respirator that we tested. Electrostatic potential measurement of the filtration layer is a key indicator for predicting filtration efficiency loss.

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