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1.
Sci Total Environ ; 892: 164683, 2023 Sep 20.
Article in English | MEDLINE | ID: covidwho-20234782

ABSTRACT

The COVID-19 pandemic generated a new source of plastic mass pollution, i.e. surgical masks, that preferentially accumulate in intertidal environments. Made of polymers, surgical masks are likely to leach additives and impact local intertidal fauna. As typical endpoints of complex developmental and physiological functions, behavioral properties are non-invasive key variables that are particularly studied in ecotoxicological and pharmacological studies, but have, first and foremost, adaptive ecological significance. In an era of ever-growing plastic pollution, this study focused on anxiety behaviors, i.e. startle response, scototaxis (i.e. preference for dark or light areas), thigmotaxis (i.e. preference for moving toward or away from physical barriers), vigilance and level of activity, of the invasive shore crab Hemigrapsus sanguineus in response to leachate from surgical masks. We first showed that in the absence of mask leachates H. sanguineus is characterized by a short startle time, a positive scototaxis, a strong positive thigmotaxis, and an acute vigilance behavior. Specifically, a significantly higher level of activity was observed in white areas, in contrast to the lack of significant differences observed in black areas. Noticeably, the anxiety behaviors of H. sanguineus did not significantly differ after a 6-h exposure to leachate solutions of masks incubated in seawater for 6, 12, 24, 48 and 96 h. In addition, our results were consistently characterized by a high inter-individual variability. This specific feature is discussed as an adaptive behavioral trait, which - through the observed high behavioral flexibility - increases H. sanguineus resilience to contaminant exposures and ultimately contribute to its invasion success in anthropogenically-impacted environments.


Subject(s)
Brachyura , COVID-19 , Animals , Humans , Brachyura/physiology , Pandemics , Masks
2.
Tour Manag ; 97: 104734, 2023 Aug.
Article in English | MEDLINE | ID: covidwho-2308992

ABSTRACT

A comparative vignette-based experimental survey design incorporating various socio-psychological factors, linked to the Theory of Planned Behavior (TPB), the Health Belief Model (HBM) and the Domain-Specific Risk-Taking scale (DOSPERT) was carried out to test variations in eight travel-related COVID-19 protective measures on Swiss tourists' travel intentions. Among the tested measures, vaccination passports, surgical masks and quarantining are those that stand out the most, with surgical masks having the greatest acceptance and willingness to adopt while traveling. Quarantining, on the other hand, appears to have a deterrent influence on travel intentions, and vaccination passports have the lowest perceived barriers during travel, but the highest perceived benefits in mitigating the spread of the infection. The discussion of individual differences has specific implications for tourism management against the background of our empirical findings.

3.
Journal of Asian and African Studies ; 58(2):214-231, 2023.
Article in English | ProQuest Central | ID: covidwho-2254824

ABSTRACT

Facemasks have been proven an effective non-pharmaceutical measure against coronavirus disease-19. Against the backdrop of global mask shortages, Taiwan distinguished herself from other countries in that Taiwan took a whole-of-nation approach to masks and mobilized the society quickly to become self-sufficient in masks. This paper argues that successful virus securitization as a threat to national security was what enabled Taiwan to effectively mobilize the private sector to carry out the state's will in ensuring adequate mask supply. Moreover, Taiwan securitized the virus more successfully than many other countries because the virus was connected to China, the nation's existing security threat.

4.
ACS Applied Polymer Materials ; 2023.
Article in English | Scopus | ID: covidwho-2286853

ABSTRACT

The Covid-19 crisis has led to a massive surge in the use of surgical masks worldwide, causing risks of shortages and high pollution. Various decontamination techniques are currently being studied to reduce these risks by allowing the reuse of masks. In this study, surgical masks were washed up to 10 times, each cycle under the same conditions. The consequences of the washing cycles on the structure, fiber morphology, and surface chemistry have been studied through several characterization techniques: scanning electron microscopy, wetting angle measurements, infrared spectroscopy, X-ray diffraction, and X-ray photoelectrons spectroscopy. The washing process did not induce large changes in the hydrophobicity of the surface, the contact angle remaining constant throughout the cycles. The composition observed in the IR spectrum also remained unchanged for washed masks up to 10 cycles. Some slight variations were observed during X-ray analysis: the crystallinity of the fibers as well as the size of the crystals increases with the number of wash cycles. The XPS analysis shows that after 10 cycles, the surface of the masks underwent a slight oxidation. In the SEM images, changes were observed in the arrangement of the fibers, which are more visible the more times the mask has been washed: they align themselves in bundles, form areas with holes in the mask layer, and are crushed in some areas. © 2023 American Chemical Society

5.
Annual Review of Fluid Mechanics ; 55:193-211, 2023.
Article in English | Web of Science | ID: covidwho-2233356

ABSTRACT

Although face masks have been used for over a century to provide protection against airborne pathogens and pollutants, close scrutiny of their effectiveness has peaked in the past two years in response to the COVID-19 pandemic. The simplicity of face masks belies the complexity of the physical phenomena that determine their effectiveness as a defense against airborne infections. This complexity is rooted in the fact that the effectiveness of face masks depends on the combined effects of respiratory aerodynamics, filtration flow physics, droplet dynamics and their interactions with porous materials, structural dynamics, physiology, and even human behavior. At its core, however, the face mask is a flow-handling device, and in the current review, we take a flow physics-centric view of face masks and the key phenomena that underlie their function. We summarize the state of the art in experimental measurements, as well as the growing body of computational studies that have contributed to our understanding of the factors that determine the effectiveness of face masks. The review also lays out some of the important open questions and technical challenges associated with the effectiveness of face masks.

6.
Cogn Process ; 24(2): 233-243, 2023 May.
Article in English | MEDLINE | ID: covidwho-2234429

ABSTRACT

Considering the global pandemic we currently experience, face masks have become standard in our daily routine. Even though surgical masks are established as a safety measure against the dissemination of COVID-19, previous research showed that their wearing compromises face recognition. Consequently, the capacity to remember to whom we transmit information-destination memory-could also be compromised. In our study, through a between-participants design (experiment 1) and a within-participants design (experiment 2), undergraduate students have to transmit Portuguese proverbs to masked and unmasked celebrity faces. Following our hypothesis, participants who shared information with masked faces had worse destination memory performance than those who shared information with unmasked faces. Also, we observed lower recognition for masked faces compared to unmasked faces. These results were expected since using a surgical mask affects facial recognition, thus making it harder to recognize a person to whom information was previously transmitted. More importantly, these results also support the idea that variables associated with the recipient's face are important for destination memory performance.


Subject(s)
COVID-19 , Humans , Masks , Pandemics , Mental Recall , Recognition, Psychology
7.
J Taiwan Inst Chem Eng ; 144: 104732, 2023 Mar.
Article in English | MEDLINE | ID: covidwho-2228739

ABSTRACT

Background: The COVID-19 pandemic has leveraged facial masks to be one of the most effective measures to prevent the spread of the virus, which thereby has exponentially increased the usage of facial masks that lead to medical waste mismanagements which pose a serious threat to life. Thermal degradation or pyrolysis is an effective treatment method for the used facial mask wastes and this study aims to investigate the thermal degradation of the same. Methods: Predicted the TGA experimental curves of the mask components using a Machine Learning model known as Artificial Neural Network (ANN). Significant findings: Three different parts of the mask namely- ribbon, body, and corner were separated and used for the analysis. The thermal degradation behavior is studied using Thermogravimetric Analysis (TGA) and this is crucial for determining the reactivity of the individual mask components as they are subjected to a range of temperatures. Using the curves obtained from TGA, kinetic parameters such as Activation energy (E) and Pre-exponential factor (A) were estimated using the Coats-Redfern model-fitting method. Using the determined kinetic parameters, thermodynamic quantities such as a change in Enthalpy (ΔH), Entropy (ΔS), and Gibbs-Free energy (ΔG) were also calculated. Since TGA is a costly and time-consuming process, this study attempted to predict the TGA experimental curves of the mask components using a Machine Learning model known as Artificial Neural Network (ANN). The dataset obtained at a heating rate of 10°C/min was used to train the 3 different neural networks corresponding to the mask components and it showed an excellent agreement with experimental data (R2 > 0.99). Through this study, a complex chemical process such as thermal degradation was modelled using Machine Learning based on available experimental parameters without delving into the intricacies and complexities of the process.

8.
New Microbes New Infect ; 52: 101090, 2023 Mar.
Article in English | MEDLINE | ID: covidwho-2211188

ABSTRACT

Background: During the Coronavirus Pandemic, the use of masks has increased significantly. The lack of control on hygiene protocols and the need to use PPE properly increases the spread of bacterial infection. The purpose of this study was to investigate the degree of contamination and frequency of bacterial species isolated from surgical and N95 masks used by hospital personnel. Methods: A total number of 175 masks were collected from staff working in Sina hospital (Hamadan province, Iran) during the first six months of 2022. The bacterial contamination of masks were evaluated and identified using biochemical kits. Antimicrobial susceptibility testing of the isolates were done using Kirby-Bauer methods and MIC were assessed for each isolate against different disinfectants (Sodium hypochlorite 5%, Hydrogen Peroxide 3%, Ethanol 70% and Deconex). Results: Of 175 masks, 471 bacterial isolates were detected including 9 species. The most prevalent strain were Coagulase negative Staphylococcus (28%) followed by Acinetobacter (20.8%) and Pseudomonas (13.8%), while, Klebsiealla and Enterococcus were the least frequent species with the rate of 3.8% and 1.2%, respectively. The results of MIC methods indicated that all 471 strains were resistant to ehtanol70% and sensitive to hydrogen peroxide 3%. Furthermore, the mean average of Deconex inhibitory effect is lower than Sodium hypochlorite 5%. Conclusions: According to the results of this study, there was a high prevalence of CoNS, Acinetobacter and Pseudomonas in hospital with a high resistance pattern against antibiotics especially Ampicillin and disinfectants.

9.
Build Environ ; 229: 109893, 2023 Feb 01.
Article in English | MEDLINE | ID: covidwho-2149422

ABSTRACT

The COVID-19 pandemic has significantly changed people's lifestyles, and wearing surgical masks in outdoor public spaces has become commonplace. However, few studies have explored the impact of wearing masks on outdoor thermal comfort in different seasons. From May 2021 to February 2022, a series of longitudinal experiments were conducted in Xiamen, China to examine the effect of wearing surgical masks on outdoor thermal comfort. Forty-two participants took part in the experiments with and without masks. During the experiments, the thermal perceptions of the subjects and environmental thermal parameters were collected. Differences in outdoor thermal comfort between subjects wearing masks and those not wearing masks were determined in summer, autumn, and winter. Results showed that 1) the subjects wearing masks had lower neutral temperatures, and this difference was particularly pronounced in summer and exacerbated by walking; 2) in warm environments, masks reduced thermal comfort, and discomfort associated with masks was worse when walking than when sitting; 3) wearing masks significantly worsened facial comfort and increased chest discomfort, as summer turned to winter, the impact of masks on facial comfort decreased; 4) radiation and air temperature were the environmental parameters with the greatest impact on outdoor thermal sensation. Subjects who wore masks preferred lower temperatures, radiation, and humidity, and higher wind speeds.

10.
Journal of Asian & African Studies (Sage Publications, Ltd.) ; : 1, 2022.
Article in English | Academic Search Complete | ID: covidwho-2112957

ABSTRACT

Facemasks have been proven an effective non-pharmaceutical measure against coronavirus disease-19. Against the backdrop of global mask shortages, Taiwan distinguished herself from other countries in that Taiwan took a whole-of-nation approach to masks and mobilized the society quickly to become self-sufficient in masks. This paper argues that successful virus securitization as a threat to national security was what enabled Taiwan to effectively mobilize the private sector to carry out the state’s will in ensuring adequate mask supply. Moreover, Taiwan securitized the virus more successfully than many other countries because the virus was connected to China, the nation’s existing security threat. [ FROM AUTHOR]

11.
Journal of Hazardous Materials ; : 130381, 2022.
Article in English | ScienceDirect | ID: covidwho-2105354

ABSTRACT

Abundant disposable surgical masks (SMs) remain in the environment and continue to age under urban environmental stressors. This study aimed to investigate the aging characteristics of SMs and the effect of different aged layers of SMs on phenanthrene (PHE), tylosin (TYL), and sulfamethazine (SMT) under two different urban environmental stressors (UV and ozone). The results show that UV exposure causes more severe aging of the SM layers than ozone. The middle layer, made of melt-brown fabric, has displayed the highest degree of aging due to its smaller diameter and mechanical strength. The two-dimensional correlation spectroscopy (2D-COS) analysis reveals the different aging sequences of functional groups and three layers in aged SMs under the two urban environmental stressors. Whether the SMs are aged or not, the adsorptions of three organic pollutants on SMs are positively correlated with the octanol-water partition coefficient. Furthermore, except for the dominant hydrophobic interaction, aged SMs can promote the adsorption of three organic pollutants by accessory interactions (hydrogen bonding and partition), depending on their structures. These findings highlight the environmental effects of new microplastic (MP) sources and coexisting pollutants under the influence of COVID-19, which is helpful in accurately evaluating the biological toxicity of SMs.

12.
Front Psychol ; 13: 960941, 2022.
Article in English | MEDLINE | ID: covidwho-2080254

ABSTRACT

Considering the current state of the worldwide pandemic, it is still common to encounter people wearing face protection masks. Although a safety measure against COVID-19, face masks might be compromising our capacity for face recognition. We conducted an online study where 140 participants observed masked and unmasked faces in a within-subjects design and then performed a recognition memory task. The best performance was found when there were no masks either at study and test phase, i.e., at the congruent unmasked condition. The worst performance was found for faces encoded with a mask but tested without it (i.e., masked-unmasked incongruent condition), which can be explained by the disruption in holistic face processing and the violation of the encoding specificity principle. Interestingly, considering the unmasked-masked incongruent condition, performance was probably affected by the violation of the encoding specificity principle but protected by holistic processing that occurred during encoding.

13.
Sci Total Environ ; 851(Pt 2): 158396, 2022 Dec 10.
Article in English | MEDLINE | ID: covidwho-2004491

ABSTRACT

Billions of disposable face masks (i.e., single-use masks) are used and discarded worldwide monthly due to the COVID-19 outbreak. The immethodical disposal of these polymer-based wastes containing non-biodegradable constituents (e.g., polypropylene) has provoked marked and severe damage to the ecosystem. Meanwhile, their ever-growing usage significantly strains the present-day waste management measures such as landfilling and incineration, resulting in large quantities of used face-covering masks landing in the environment as importunate contaminants. Hence, alternative waste management strategies are crucially demanded to decrease the negative impacts of face mask contamination. In this venue, developing high-yield, effective, and green routes toward recycling or upcycling face mask wastes (FMWs) into value-added materials is of great importance. While existing recycling processes assist the traditional waste management, they typically end up in materials with downgraded physicochemical, structural, mechanical, and thermal characteristics with reduced values. Therefore, pursuing potential economic upcycling processes would be more beneficial than waste disposal and/or recycling processes. This paper reviews recent advances in the FMWs upcycling methods. In particular, we focus on producing value-added materials via various waste conversion methods, including carbonization (i.e., extreme pyrolysis), pyrolysis (i.e., rapid carbonization), catalytic conversion, chemical treatment, and mechanical reprocessing. Generally, the upcycling methods are promising, firming the vital role of managing FMWs' fate and shedding light on the road of state-of-the-art materials design and synthesis.


Subject(s)
COVID-19 , Masks , Humans , Ecosystem , Polypropylenes , Recycling/methods , Plastics
14.
J Hosp Infect ; 115: 64-70, 2021 Sep.
Article in English | MEDLINE | ID: covidwho-1271691

ABSTRACT

BACKGROUND: It is difficult to make a lace-up surgical mask fit tightly to the face with conventional wearing methods because of the strings' poor tension, resulting in some air flowing through the gap. We introduced two feasible new wearing methods and obtained satisfactory experimental results. METHODS: The wearing of surgical masks by staff was investigated through observation and interview in operation rooms. The required time to don, close-fitting rates, and satisfaction of the conventional method and the two new recommended methods were counted and compared, according to the subjects' experience. The differences between the three wearing methods on the microbial contamination of the sterile area were explored in a mock operation. RESULTS: In the subjects' experience, the close-fitting rates were 47.0%, 92.0% and 100.0% in the conventional, Three Knots, and Elastic Band groups, respectively (P<0.001); the satisfaction scores evaluated by numerical rating scale from 0 to 10 were 5.06 ± 2.22, 6.89 ± 1.86 and 7.10 ± 1.72, respectively (P<0.001); the required times were 14.32 ± 2.20, 25.76 ± 5.13 and 27.37 ± 5.11 s, respectively (P<0.001). In the mock operation, there were significant differences between the conventional and Three Knots groups (37.5 (13) vs 18 (8) cfu, P<0.001), as well as between the conventional and Elastic Band groups (37.5 (13) vs 17(10) cfu, P<0.001). CONCLUSIONS: The recommended new wearing methods had the advantages of closer fit, higher satisfaction rates, were more comfortable, and resulted in lower contamination of the sterile area; however, the recommended two methods required more time.


Subject(s)
Masks , Operating Rooms , Humans
15.
Appl Acoust ; 197: 108940, 2022 Aug.
Article in English | MEDLINE | ID: covidwho-1956084

ABSTRACT

With the COVID-19 pandemic, the usage of personal protective equipment (PPE) has become 'the new normal'. Both surgical masks and N95 masks with a face shield are widely used in healthcare settings to reduce virus transmission, but the use of these masks has a negative impact on speech perception. Therefore, transparent masks are recommended to solve this dilemma. However, there is a lack of quantitative studies regarding the effect of PPE on speech perception. This study aims to compare the effect on speech perception of different types of PPE (surgical masks, N95 masks with face shield and transparent masks) in healthcare settings, for listeners with normal hearing in the audiovisual or auditory-only modality. The Bamford-Kowal-Bench (BKB)-like Mandarin speech stimuli were digitally recorded by a G.R.A.S KEMAR manikin without and with masks (surgical masks, N95 masks with face shield and transparent masks). Two variants of video display were created (with or without visual cues) and tagged to the corresponding audio recordings. The speech recording and video were presented to listeners simultaneously in each of four conditions: unattenuated speech with visual cues (no mask); surgical mask attenuated speech without visual cues; N95 mask with face shield attenuated speech without visual cues; and transparent mask attenuated speech with visual cues. The signal-to-noise ratio for 50 % correct scores (SNR50) threshold in noise was measured for each condition in the presence of four-talker babble. Twenty-four subjects completed the experiment. Acoustic spectra obtained from all types of masks were primarily attenuated at high frequencies, beyond 3 kHz, but to different extents. The mean SNR50 thresholds of the two auditory-only conditions (surgical mask and N95 mask with face shield) were higher than those of the audiovisual conditions (no mask and transparent mask). SNR50 thresholds in the surgical-mask conditions were significantly lower than those for the N95 masks with face shield. No significant difference was observed between the two audiovisual conditions. The results confirm that wearing a surgical mask or an N95 mask with face shield has a negative impact on speech perception. However, wearing a transparent mask improved speech perception to a similar level as unmasked condition for young normal-hearing listeners.

16.
Neuropsychologia ; 174: 108334, 2022 09 09.
Article in English | MEDLINE | ID: covidwho-1937048

ABSTRACT

In the last two years, face-to-face interactions have drastically changed worldwide, because of the COVID-19 pandemic: the persistent use of masks has had the advantage of reducing viral transmission, but it has also had the cost of impacting on the perception and recognition of social information from faces, especially emotions. To assess the cerebral counterpart to this condition, we carried out an EEG experiment, extracting Event-Related Potentials (ERPs) evoked by emotional faces with and without surgical masks. Besides the expected impairment in emotion recognition in both accuracy and response times, also the classical face-related ERPs (N170 and P2) are altered by the presence of surgical masks. Importantly, the effect is stronger in individuals with a lower daily exposure to masks, suggesting that the brain must adapt to an extra constraint in decoding social input, due to masks hiding crucial facial information.


Subject(s)
COVID-19 , Facial Recognition , Electroencephalography , Emotions/physiology , Evoked Potentials/physiology , Facial Expression , Facial Recognition/physiology , Humans , Pandemics
17.
Journal of Environmental Chemical Engineering ; : 108241, 2022.
Article in English | ScienceDirect | ID: covidwho-1926624

ABSTRACT

Numerous disposable surgical masks (DSMs) were consumed with the development of COVID-19 epidemic. Non-solid products recovered by pyrolysis is more than twenty species with low added value. Therefore, the search for a reasonable carbonization method can not only alleviate the pressure of global plastic pollution, but also produce considerable economic value. Here it is found that microwave cross-linking can promote the substitution of hydrogen atom in the polymer master chain of DSMs by hydrogen atom, which can reorganize the easily cracked DSMs into sp2-hybridized aromatic carbon, it can maintain 51.2% carbon yield at 1000℃. The difference between the DSMs-based porous carbon obtained by in-situ and post-processing N doping was further compared, and it was found that the specific surface area of the activated in-situ doped sample (P-SNO@DSMs) was as high as 2278 m2·g-1, which had rich hierarchical pore structure and high heteroatoms doping rate. Benefiting from the synergistic effect of heteroatoms and hierarchical holes, P-SNO@DSMs sulfur cathode delivers a high specific capacity of 1550 mAh·g-1 at 0.1C and exhibits excellent long-term cycling performance with the smaller capacity decay of 0.13% per cycle after 400 cycles. In this work, clean and efficient microwave cross-linking not only realized the efficient recovery of waste DSMs, but also the application of the prepared materials can be broadened by adding additional heteroatomic sources in the process of microwave cross-linking.

18.
Journal of Complementary Medicine Research ; 13(1):12-16, 2022.
Article in English | Web of Science | ID: covidwho-1856109

ABSTRACT

Objective: According to recent studies and systematic review and meta-analysis, there is not enough evidence to determine which has a positive effect on COVID-19 epidemics, and the number of articles is very low. Therefore, the present study aims to compare the efficiency of positive results between N95 respirators and medical masks. Methods: Among the electronic databases, we selected Cochrane Library, PubMed, ISI, and Embas for systematically review the publications from 2010 to 2020. We then applied a software program called Endnote X8 to investigate the electronic topics and used mesh terms and concepts for searching. Log risk-ratio between both groups (N95 respirators & medical masks) with 95% confidence interval (CI), Mantel-Haenszel method as well as fixed effect model were computed. Moreover, we employed a commercial software program called Comprehensive Meta-Analysis Stata 16 for evaluating forest plots and meta-analysis. Results: Totally, we observed 27 s and topics with the potential relevance in the course of the manual and electronic searches so that three papers matched our inclusion criteria for performing a systematic review. Risk ratio equaled (RR, 0.01 95% CI 0.00, 0.02. P= 0.07), showing that using N95 respirators and medical masks did not significantly differ in preventing respiratory viral infections. Moreover, Using N95 respirators and medical masks did not significantly differ in preventing bacterial colonization (p=0.02). Conclusion: This research revealed a positive impact of both N95 respirators and medical masks for COVID-19.

19.
Speech Communication ; 139:45-50, 2022.
Article in English | Web of Science | ID: covidwho-1852085

ABSTRACT

Wearing a facemask impacts oral communication as it is both a barrier to the acoustic signal and occludes nonverbal cues such as lip movements and facial expressions. However, while past studies have suggested that these factors do not cause significant impediments to comprehension among speakers of the same first language, the current study investigates the impact facemasks have in the context of second language learners. N = 192 participants were divided into three groups of n = 64 and asked to listen to an 89 s speech. To isolate the effects of visual cues on listening comprehension, the same audio recording was used for all experimental groups. Condition One was a video of a speaker with no mask. Condition Two was a video of the same speaker wearing a mask. Condition Three was an audio recording. The significant finding was that participants in the second (masked) condition scored significantly lower on subsequent comprehension quizzes than the other two. Implications to language instruction during the COVID-19 pandemic will be discussed.& nbsp;

20.
Sep Purif Technol ; 294: 121180, 2022 Aug 01.
Article in English | MEDLINE | ID: covidwho-1815164

ABSTRACT

The outbreak of SARS-CoV-2 pandemic highlighted the worldwide lack of surgical masks and personal protective equipment, which represent the main defense available against respiratory diseases as COVID-19. At the time, masks shortage was dramatic in Italy, the first European country seriously hit by the pandemic: aiming to address the emergency and to support the Italian industrial reconversion to the production of surgical masks, a multidisciplinary team of the University of Bologna organized a laboratory to test surgical masks according to European regulations. The group, driven by the expertise of chemical engineers, microbiologists, and occupational physicians, set-up the test lines to perform all the functional tests required. The laboratory started its activity on late March 2020, and as of the end of December of the same year 435 surgical mask prototypes were tested, with only 42 masks compliant to the European standard. From the analysis of the materials used, as well as of the production methods, it was found that a compliant surgical mask is most likely composed of three layers, a central meltblown filtration layer and two external spunbond comfort layers. An increase in the material thickness (grammage), or in the number of layers, does not improve the filtration efficiency, but leads to poor breathability, indicating that filtration depends not only on pure size exclusion, but other mechanisms are taking place (driven by electrostatic charge). The study critically reviewed the European standard procedures, identifying the weak aspects; among the others, the control of aerosol droplet size during the bacterial filtration test results to be crucial, since it can change the classification of a mask when its performance lies near to the limiting values of 95 or 98%.

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