scholarly journals Ethanol-Drying Regeneration of N95 Respirators

Author(s):  
Albert I. Nazeeri ◽  
Isaac A. Hilburn ◽  
Daw-An Wu ◽  
Kabir A. Mohammed ◽  
D. Yovan Badal ◽  
...  

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.

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258191
Author(s):  
Scott Duncan ◽  
Paul Bodurtha ◽  
Syed Naqvi

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.


Author(s):  
Amrita R. John ◽  
Shine Raju ◽  
Jennifer L. Cadnum ◽  
Kipum Lee ◽  
Phillip McClellan ◽  
...  

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.


Author(s):  
Simeon C. Daeschler ◽  
Niclas Manson ◽  
Kariym Joachim ◽  
Alex W. H. Chin ◽  
Katelyn Chan ◽  
...  

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.


2021 ◽  
Author(s):  
Xin Zhang ◽  
Ruge Quhe ◽  
Ming Lei

Abstract The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear. In this paper, water and oxygen molecule adsorptions on the all-inorganic perovskite (CsPbBr3) surface are studied by density-functional theory calculations. In terms of the adsorption energy, the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr3 surface. The water molecules can be adsorbed on both the CsBr- and PbBr-terminated surfaces, but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference. While the adsorbed water molecules only contribute deep states, the oxygen molecules introduce interfacial states inside the bandgap of the perovskite, which would significantly impact the chemical and transport properties of the perovskite. Therefore, special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr3 based devices.


2013 ◽  
Vol 643 ◽  
pp. 120-124
Author(s):  
Yi Jui Chiu ◽  
Chia Hao Yang ◽  
Luh Maan Chang ◽  
Khai Shoon Leong

This paper aims to develop in the semiconductor plant molecular filtration efficiency with properties of semiconductor materials in the real-time. The goal of the assessment is to propose a new device based on the technologies assessed. First, the Scanning Mobility Particle Sizer Spectrometer with CPC (SMPS+C), a description of how each counter works is given. Second, a new experiment method for HEPA/ULPA filter efficiency certification in the real-time in semiconductor industry is developed. The experimental results showed that the performance of capillary had been installed and cleaned. The SMPS mean diameter fell within the range of the NIST standard. And, the HEPA/ULPA filter efficiency certification is explored. The best filtration efficiency particles size is 0.16μm. The results of this research provide the engineers with very useful information in semiconductor industry.


2021 ◽  
pp. 152808372110287
Author(s):  
Amit Kumar ◽  
Basundhara Bhattacharjee ◽  
DN Sangeetha ◽  
V Subramanian ◽  
B Venkatraman

Due to the ongoing pandemic, various types of facemasks such as certified N-95, non-woven fiber and fabric/textile masks are being used as an essential protective measure to reduce the risk of spread of the SARS-Cov-2 virus. The aerosols size-dependent filtration efficiency and breathing resistance of these masks were tested before and after sterilization by five different methods for two flow rates (20 and 90 L/min) conditions corresponding to regular breathing rate and moderate/strenuous exertion, in the particle size range 0.3–10 µm. Sterilization techniques used here are autoclaving (30 and 60 minutes), dry air oven heating (30 and 60 minutes), ionizing irradiation (15 and 25 kGy), hot water washing with and without detergent and immersing in a 10% concentration of liquid hydrogen peroxide for 30 minutes. Further, the filtration efficiency of each type of masks is also studied with laboratory generated two-order higher aerosol concertation. The certified mask has the most outstanding filtering efficiency among all the other type of facemasks. The ionizing radiation causes a significant reduction in filtration efficacy, so that it is not recommended for sterilization purpose. The best method to sterilize certified N-95 masks without affecting their performance is by using dry air heating with temperature ranging from 70–80 °C. The performance of the cloth and surgical masks is found to be comparable for both flow conditions. As an affordable sterilization method, hot water washing is recommended, which does not deteriorate the fabric masks efficiency and can be used by the common people. The recommended masks for the general people are textile/fabric masks which serves fit for the purpose than non-woven masks because it can help to reduce non-biodegradable waste (facemask) and prevent respiratory droplet transmission. The non-woven mask can be sterilized with dry heat, hot water wash and autoclave.


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 ◽  
...  

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.


2021 ◽  
Vol 8 ◽  
Author(s):  
Connor Stahl ◽  
Kevin Frederick ◽  
Sachin Chaudhary ◽  
Christopher J. Morton ◽  
Douglas Loy ◽  
...  

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic can spread through virus-containing aerosols ( ≤ 5 μm) and larger airborne droplets. Quantifying filtration efficiency of different kinds of masks and linings for aerosols that fall within the most penetrating particle size (80-400 nm) is critical to limiting viral transmission. The objective of our experiment was to compare the “real-world” filtering efficiency of different face masks for fine aerosols (350 nm) in laboratory simulations.Methods: We performed a simulated bench test that measured the filtering efficiency of N95 vs. N99 masks with elastomeric lining in relation to baseline (“background”) aerosol generation. A mannequin head was placed within a chamber and was attached to an artificial lung simulator. Particles of known size (350 ± 6 nm aerodynamic diameter) were aerosolized into the chamber while simulating breathing at physiological settings of tidal volume, respiratory rate, and airflow. Particle counts were measured between the mannequin head and the lung simulator at the tracheal airway location.Results: Baseline particle counts without a filter (background) were 2,935 ± 555 (SD) cm−3, while the N95 (1348 ± 92 cm−3) and N99 mask with elastomeric lining (279 ± 164 cm−3; p &lt;0.0001) exhibit lower counts due to filtration.Conclusion: The filtration efficiency of the N95 (54.1%) and N99 (90.5%) masks were lower than the filtration efficiency rating. N99 masks with elastomeric lining exhibit greater filtration efficiency than N95 masks without elastomeric lining and may be preferred to contain the spread of SARS-CoV-2 infection.


Author(s):  
Ebru Oral ◽  
Keith K. Wannomae ◽  
Rachel Connolly ◽  
Joseph Gardecki ◽  
Hui Min Leung ◽  
...  

There are a variety of methods routinely used in the sterilization of medical devices using hydrogen peroxide (H2O2) including vaporization, plasma generation and ionization. Many of these systems are used for sterilization and are validated for bioburden reduction using bacterial spores.Here, we explored the benefits of using vaporized H2O2 (VHP) treatment of N95 respirators for emergency decontamination and reuse to alleviate PPE shortages for healthcare workers in the COVID-19 emergency. The factors that are considered for the effective reuse of these respirators are the fit, the filter efficiency and the decontamination/disinfection level for SARS-CoV-2, which is the causative virus for COVID-19 and other organisms of concern in the hospital environment such as methicillin-resistant Staphylococcus aureus or Clostridium difficile. WE showed that the method did not affect fit or filter efficiency at least for one cycle and resulted in a >6 log reduction in bacterial spores and >3.8 log reduction in the infectious SARS-CoV2 load on N95 respirators.


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