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Bacterial filtration efficiency is the main characteristic of medical face masks effectivity and quality. The testing method is given by European and US, respectively, standard. The method is based on the analysis of biological aerosol with the bacterium Staphylococcus aureus in Andersen cascade impactor. The Andersen impactor contains six stages simulating the different parts of the respiratory tract, from the upper part with the larger droplets to the lungs with the small aerosol particles of the submicron size. The particles are separated depending on the size and sediment on agar medium in Petri dishes filled in the impactor. The use of the glass Petri dishes is recommended for the Andersen impactor, but the most of laboratories prefer the disposable plastic dishes, actually. The evaluation of the use of plastic dishes in Andersen impactor for the determination of the bacterial filtration efficiency of the medical face masks is the aim of this study.

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As a result of the COVID-19 pandemic, many new materials and masks came onto the market. To determine their suitability, several standards specify which properties to test, including bacterial filtration efficiency (BFE), while none describe how to determine viral filtration efficiency (VFE), a property that is particularly important in times of pandemic. Therefore, we focused our research on evaluating the suitability and efficiency of different systems for determining VFE. Here, we evaluated the VFE of 6 mask types (e.g., a surgical mask, a respirator, material for mask production, and cloth masks) with different filtration efficiencies in four experimental setups and compared the results with BFE results. The study included 17 BFE and 22 VFE experiments with 73 and 81 mask samples tested, respectively. We have shown that the masks tested had high VFE (>99% for surgical masks and respirators, ≥98% for material, and 87-97% for cloth masks) and that all experimental setups provided highly reproducible and reliable VFE results (coefficient of variation < 6%). Therefore, the VFE tests described in this study can be integrated into existing standards for mask testing.

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Observational evidence suggests that mask-wearing mitigates transmission of COVID-19; at the same time high respiratory resistance leads to an unwillingness to wear masks. This paper proposed a respiratory drive structure to reduce the air resistance of a mask. This structure provides different shapes during expiration and inspiration while focusing on filtering dust, bacteria, or viruses. Meanwhile, the assembled system on the mask can be disassembled and replaced. Then porous media simulation is used to verify the model effect. Experimental results of a new mask show that the ventilation resistance is reduced by 20%, and the bacterial filtration efficiency meets the requirements of YY 0469-2011.

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PURPOSE: To evaluate the choroidal thickness (CT) with enhanced depth-imaging optical coherence tomography (EDI-OCT) in healthcare professionals using surgical masks or FFP2 (N95) masks. METHODS: We included the 120 eyes of 120 healthy volunteers who were using a surgical mask (Group 1) or FFP2 mask (Group 2) in the study. Spectral domain (SD) OCT was used to measure CT. EDI-OCT was used to measure subfoveal and perifoveal CT. Points 1500 µm nasal (CN1500) and temporal (CT1500) to the foveal center were used to measure perifoveal CT. Oxygen saturation and heart rate were measured with a pulse oximeter. All measurements were performed at 8:30, before wearing the mask, and at 12:30, when the mask was removed for the lunch break. RESULTS: Of a total of 120 subjects, Group 1 consisted of 60 subjects (mean age 38.50±8.60 (range 24-44) years) and Group 2 also consisted of 60 subjects (mean age 36.60±6.53 (range 26-45) years). Although not statistically significant, CT was seen to have increased at 3 measurement points in Group 1 after using the mask for 4 h: subfoveal CT (CSF) (p = 0.545), CT1500 (p = 0.080), and CN1500 (p = 0.251)). In Group 2, the increase in CSF (p = 0.001) was statistically significant while the increases in CN1500 and CT1500 were not (p = 0.162 and p = 0.058, respectively) after using the mask for 4 h. CONCLUSION: We found CT to increase after 4 h of mask use, and this increase was more marked in Group 2. The increase in subfoveal CT in particular was statistically significant in Group 2.

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With the ongoing COVID-19 pandemic, reusable high-performance cloth masks are recommended for the public to minimize virus spread and alleviate the demand for disposable surgical masks. However, the approach to design a high-performance cotton mask is still unclear. In this study, we aimed to find out the relationship between fabric properties and mask performance via experimental design and machine learning. Our work is the first reported work of employing machine learning to develop protective face masks. Here, we analyzed the characteristics of Egyptian cotton (EC) fabrics with different thread counts and measured the efficacy of triple-layered masks with different layer combinations and stacking orders. The filtration efficiencies of the triple-layered masks were related to the cotton properties and the layer combination. Stacking EC fabrics in the order of thread count 100-300-100 provides the best particle filtration efficiency (45.4%) and bacterial filtration efficiency (98.1%). Furthermore, these key performance metrics were correctly predicted using machine-learning models based on the physical characteristics of the constituent EC layers using Lasso and XGBoost machine-learning models. Our work showed that the machine learning-based prediction approach can be generalized to other material design problems to improve the efficiency of product development.

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Polyvinylidene fluoride (PVDF) blended with varying concentrations of titanium nanotubes (TNT) was electrospun to result in a nanocomposite filter media. Sandwich structures were obtained by depositing the electrospun fibers between polypropylene (PP) nonwoven sheets. The synthesized tubular TNT was confirmed for its morphology through a transmission electron microscope (TEM). The prepared filter media was analyzed through a scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The effectiveness of the filter media was evaluated through the zone of inhibition and antibacterial activity against E. coli and S. aureus. The Box-Behnken design is experimented with three-level variables, namely areal density of substrate (GSM), electrospinning time (hours), and concentration of TNT (wt%) for investigating the bacterial filtration efficiency through an Andersen sampler. Among other statistical tests (STATs), PVDF + 15 wt% TNT has a bacterial filtration efficiency of 99.88% providing greater potentials upon application for clean air management. It can be noted that the future application of this formulation could be efficient filtration of other microbes and could be used in facemasks to industrial-scale air filters. Graphical abstract.

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The first wave of the COVID-19 pandemic brought about a broader use of masks by both professionals and the general population. This resulted in a severe worldwide shortage of devices and the need to increase import and activate production of safe and effective surgical masks at the national level. In order to support the demand for testing surgical masks in the Italian context, Universities provided their contribution by setting up laboratories for testing mask performance before releasing products into the national market. This paper reports the effort of seven Italian university laboratories who set up facilities for testing face masks during the emergency period of the COVID-19 pandemic. Measurement set-ups were built, adapting the methods specified in the EN 14683:2019+AC. Data on differential pressure (DP) and bacterial filtration efficiency (BFE) of 120 masks, including different materials and designs, were collected over three months. More than 60% of the masks satisfied requirements for DP and BFE set by the standard. Masks made of nonwoven polypropylene with at least three layers (spunbonded-meltblown-spunbonded) showed the best results, ensuring both good breathability and high filtration efficiency. The majority of the masks created with alternative materials and designs did not comply with both standard requirements, resulting in suitability only as community masks. The effective partnering between universities and industries to meet a public need in an emergency context represented a fruitful example of the so-called university "third-mission".

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The COVID-19 outbreak has resulted in a shortage of personal protective equipment (PPE) throughout the world. This shortage has resulted in an increase in production of PPE to meet the demand, and as a result, several substandard equipment has entered the market. With face masks and respirators now beginning to see widespread use throughout the world, the standards and test with which they are required to undertake have become points of interest. The filtration efficiency of the masks is a key testing element that examines its ability to filter particles, bacteria and viruses; this examines the penetration efficiency percentage of each with lower results being preferable. Masks are also subjected to NaCl testing method, which allows a range of particle sizes to be examined and their penetration to be observed. The masks must also show considerable resistance to fluids and flames, to prevent the penetration of liquids and to be non-flammable. Various PPE testing protocols such as biological, chemical, fluid and flame resistances, protective ensemble, facepiece fit testing, NIOSH NaCl method and impact protection have been discussed. In addition, various tests involving bacterial and viral filtration efficiencies are also discussed. Differential pressure is examined to ascertain the comfort, airflow and breathability of the masks, whilst fit testing is examined to ensure a correct fit of the mask.

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Many healthcare systems have been forced to outsource simple mask production due to international shortages caused by the COVID-19 pandemic. Providence created simple masks using surgical wrap and submitted samples to an environmental lab for bacterial filtration efficiency testing. Bacterial filtration efficiency rates ranged from 83.0% to 98.1% depending on specific material and ply, and particular filtration efficiency rates ranged from 92.3% to 97.7%. Based on mask configuration, specific surgical wrap selected, and ply, the recommended filtration efficiency for isolation and surgical masks of 95% and 98%, respectively can be achieved. These alternative masks can allow for similar coverage and safety when hospital-grade isolation masks are in short supply.

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OBJECTIVE: In order to find whether there is the correlation between the non-oil particle filtration efficiency(PFE) and the bacterial filtration efficiency(BFE) of medical surgical masks. METHODS: Non-oil particle filtration efficiency and bacterial filtration efficiency were compared and analyzed through the test data of medical surgical masks from 2012 to 2018. RESULTS: When the non-oil particle filtration efficiency of medical surgical mask is over 80%, the bacterial filtration efficiency can reach 95%. CONCLUSIONS: In order to reach the requirement of 95% bacterial filtration efficiency, surgical medical mask must improve the limit of non-oil particle filtration efficiency. The results of data analysis can provide reference for emergency inspection and filter material rapid inspection, and also provide reference for the revision of YY 0469 standard.

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OBJECTIVE@#In order to find whether there is the correlation between the non-oil particle filtration efficiency(PFE) and the bacterial filtration efficiency(BFE) of medical surgical masks.@*METHODS@#Non-oil particle filtration efficiency and bacterial filtration efficiency were compared and analyzed through the test data of medical surgical masks from 2012 to 2018.@*RESULTS@#When the non-oil particle filtration efficiency of medical surgical mask is over 80%, the bacterial filtration efficiency can reach 95%.@*CONCLUSIONS@#In order to reach the requirement of 95% bacterial filtration efficiency, surgical medical mask must improve the limit of non-oil particle filtration efficiency. The results of data analysis can provide reference for emergency inspection and filter material rapid inspection, and also provide reference for the revision of YY 0469 standard.

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NIOSH published a Federal Register Notice to explore the possibility of incorporating FDA required filtration tests for surgical masks (SMs) in the 42 CFR Part 84 respirator certification process. There have been no published studies comparing the filtration efficiency test methods used for NIOSH certification of N95 filtering facepiece respirators (N95 FFRs) with those used by the FDA for clearance of SMs. To address this issue, filtration efficiencies of "N95 FFRs" including six N95 FFR models and three surgical N95 FFR models, and three SM models were measured using the NIOSH NaCl aerosol test method, and FDA required particulate filtration efficiency (PFE) and bacterial filtration efficiency (BFE) methods, and viral filtration efficiency (VFE) method. Five samples of each model were tested using each method. Both PFE and BFE tests were done using unneutralized particles as per FDA guidance document. PFE was measured using 0.1 µm size polystyrene latex particles and BFE with ∼3.0 µm size particles containing Staphylococcus aureus bacteria. VFE was obtained using ∼3.0 µm size particles containing phiX 174 as the challenge virus and Escherichia coli as the host. Results showed that the efficiencies measured by the NIOSH NaCl method for "N95 FFRs" were from 98.15-99.68% compared to 99.74-99.99% for PFE, 99.62-99.9% for BFE, and 99.8-99.9% for VFE methods. Efficiencies by the NIOSH NaCl method were significantly (p = <0.05) lower than the other methods. SMs showed lower efficiencies (54.72-88.40%) than "N95 FFRs" measured by the NIOSH NaCl method, while PFE, BFE, and VFE methods produced no significant difference. The above results show that the NIOSH NaCl method is relatively conservative and is able to identify poorly performing filtration devices. The higher efficiencies obtained using PFE, BFE and VFE methods show that adding these supplemental particle penetration methods will not improve respirator certification.

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