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Simple Respiratory Protection--Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles
Abstract
A shortage of disposable filtering facepiece respirators can be expected during a pandemic respiratory infection such as influenza A. Some individuals may want to use common fabric materials for respiratory protection because of shortage or affordability reasons. To address the filtration performance of common fabric materials against nano-size particles including viruses, five major categories of fabric materials including sweatshirts, T-shirts, towels, scarves, and cloth masks were tested for polydisperse and monodisperse aerosols (20-1000 nm) at two different face velocities (5.5 and 16.5 cm s⁻¹) and compared with the penetration levels for N95 respirator filter media. The results showed that cloth masks and other fabric materials tested in the study had 40-90% instantaneous penetration levels against polydisperse NaCl aerosols employed in the National Institute for Occupational Safety and Health particulate respirator test protocol at 5.5 cm s⁻¹. Similarly, varying levels of penetrations (9-98%) were obtained for different size monodisperse NaCl aerosol particles in the 20-1000 nm range. The penetration levels of these fabric materials against both polydisperse and monodisperse aerosols were much higher than the penetrations for the control N95 respirator filter media. At 16.5 cm s⁻¹ face velocity, monodisperse aerosol penetrations slightly increased, while polydisperse aerosol penetrations showed no significant effect except one fabric mask with an increase. Results obtained in the study show that common fabric materials may provide marginal protection against nanoparticles including those in the size ranges of virus-containing particles in exhaled breath.
... The effectiveness of improvised respiratory protection is largely determined by the choice of filtration material and quality of design [27]. Readily available fabrics, including various cotton fabrics, silk, chiffon, tea towels, and surgical fabric have been repurposed as respiratory filtration systems [15,16,[28][29][30][31][32][33][34]. However, even with excellent filtration capabilities, if a mask does not fit properly, virus-containing particles can penetrate through gaps between the mask and face [35,36] leading to filtration efficiency decreases of up to 60% [29]. ...
... The origami fabrication procedure can be used with alternative materials not included here, such as other fabrics with known filtration efficacy (e.g. see [28][29][30][31][32][33][34]). ...
... Importantly, alternative materials such as other fabrics with known filtration efficacy (e.g. see [28][29][30][31][32][33]) can be used with the proposed fabrication technique. The origami fabrication procedure represents a flexible solution that can accommodate different facial sizes, and, depending on material choice, realize the full range of filtration properties allowing a user to tune improvised masks to their particular needs. ...
Respiratory aerosols with diameters smaller than 100~m have been confirmed as important vectors for the spread of diseases such as SARS-CoV-2. While disposable and cloth masks afford some protection, they are typically inefficient at filtering these aerosols and require specialized fabrication devices to produce. We describe a fabrication technique that makes use of a folding procedure (origami) to transform any filtration material into a mask. These origami masks can be fabricated by non-experts at minimal cost and effort, provide adequate filtration efficiencies, and are easily scaled to different facial sizes. Using a mannequin fit test simulator, we demonstrate that these masks can provide filtration efficiencies of over 90\% while simultaneously providing greater comfort as demonstrated by pressure drops of <~20~Pa. We also quantify mask leakage by measuring the variations in filtration efficiency and pressure drop when masks are sealed to the mannequin face compared to when the mask is unsealed but positioned to achieve the best fit. While leakage generally trended with pressure drop, some of the best performing mask media achieved <~10\% reduction in filtration efficiency due to leakage. Because this mask can provide high filtration efficiencies at low pressure drop compared to commercial alternatives, it is likely to promote greater mask wearing tolerance and acceptance.
... Most initiatives that verified filtration ability of face masks were in vitro studies that used droplet generator (>5 μm) or aerosols (≤5 μm) through masks or fabrics to assess their blocking potential. [15][16][17][18][19][20][21] Several substances were used for the production of the particles, such as sodium chloride 15,17,18 fluorescent nanoparticles 16 and polystyrene particles, 20 in addition to microorganisms such as avian influenza virus, 18 bacteriophage MS2 22 , Staphylococcus aureus 19 and Bacillus atrophaeus. 22 Some combinations of different fabrics including multiple layers showed a higher filtration ability: masks made of one or two layers of 600 threads per inch 100% cotton (over 98%); face masks of one layer of 200 threads per inch 100% cotton, (96%); 16 masks of one layer of cotton silk blend fabrics, (over 94%); 17 masks of one layer of 70% cotton and 30% polyester, (93%); 16 non-woven face masks, two layers (93%); 19 and masks of one layer of polyester and four layers of kitchen paper (95%). ...
... Most initiatives that verified filtration ability of face masks were in vitro studies that used droplet generator (>5 μm) or aerosols (≤5 μm) through masks or fabrics to assess their blocking potential. [15][16][17][18][19][20][21] Several substances were used for the production of the particles, such as sodium chloride 15,17,18 fluorescent nanoparticles 16 and polystyrene particles, 20 in addition to microorganisms such as avian influenza virus, 18 bacteriophage MS2 22 , Staphylococcus aureus 19 and Bacillus atrophaeus. 22 Some combinations of different fabrics including multiple layers showed a higher filtration ability: masks made of one or two layers of 600 threads per inch 100% cotton (over 98%); face masks of one layer of 200 threads per inch 100% cotton, (96%); 16 masks of one layer of cotton silk blend fabrics, (over 94%); 17 masks of one layer of 70% cotton and 30% polyester, (93%); 16 non-woven face masks, two layers (93%); 19 and masks of one layer of polyester and four layers of kitchen paper (95%). ...
... [17][18][19] Assays with assessment of particles of different sizes (20 to 1,000 nm) and velocity dispersion (5.5 cm/s and 16.5 cm/s) showed that 100% cotton, 100% polyester and fabrics made of cotton blends had instantaneous penetration level (the opposite of filtration), between 40 and 90%, with increased penetration according to the increase in the air velocity used. 15 At a flow 8 L/min and 19 L/min, homemade masks with plastic and latex valves had filtration efficacy above 60%, while two other homemade masks ranged from 10% to 90%. 21 At a flow of 32 L/min, cotton fabrics of weight between 157 and 360 g/m 2 showed filtration efficiency between 5% and 25%; masks of silk, 4%; surgical masks, 33%; and respirators, 95%. ...
Objective: To describe the recommendations, physical characteristics, disinfection methods and efficacy of the use of homemade face masks to reduce COVID-19 transmission. Methods: We searched MEDLINE, SciELO, and Google Scholar, in addition to the official recommendations for the use of masks. Results: Thirty-one references were included. Fabric filtration efficiency ranged from 5% to 98%. The filtration efficacy of three layered 100% cotton fabric face masks ranged from 70% and 99% in vitro studies. Homemade, surgical, and respirator masks showed breathability between 2.2 and 3.0 Pascal. The capacity to reduce the spread of microorganisms by people wearing homemade face masks was three times lower when compared to those wearing surgical masks, although this capacity was higher when compared to those who did not wear masks. Conclusion: The breathability of homemade masks proved to be adequate, while the filtration ability seemed to be lower than that of surgical masks, but it was better than not wearing any masks at all. There is no evidence to support the efficacy and effectiveness of homemade masks.
... This could increase the relevance of the data, but the unique testing protocol makes it difficult to compare results with those of other studies. Rengasamy et al. also found towels to be one of the most effective filters among common household textiles, though it is not clear if the towels tested were tea towels, or something closer to bath towels [57]. ...
... Fabrics from common consumer items were tested for filtration efficiency using 0.02-1.0 µm particles [57]. The test included two different velocities, and both polydisperse and monodisperse particles and the fabrics were compared with surgical masks, dust masks, and an N95 respirator. ...
... Sweatshirts, T-shirts, towels, and scarves, as well as fabric face coverings allowed at least 50% penetration of the particles, with the exception of one poly/cotton sweatshirt with 40% penetration at low velocity. Towels generally provide greater filtration than other apparel items [57]. The paper provides no explanation for this, and the only descriptive information provided about fabrics is fiber content. ...
Textile supply chain challenges due to the COVID-19 pandemic and the Russia-Ukraine war give unique insights into how health crises and geopolitical instability could dry up supplies of vital materials for the smooth functioning of human societies in calamitous times. Coinciding adverse global events or future pandemics could create shortages of traditional face coverings among other vital materials. Reusable face coverings could be a viable relief option in such situations. This review identifies the lack of studies in the existing literature on reusable fabric face coverings available in the market. It focuses on the development, filtration mechanisms, and factors associated with the filtration efficiency of reusable knitted and woven fabric face coverings. The authors identified relevant papers through the Summon database. Keeping the focus on readily available fabrics, this paper encompasses the key aspects of reusable face coverings made of knitted and woven fabrics outlining filtration mechanisms and requirements, development, factors affecting filtration performance, challenges, and outcomes of clinical trials. Filtration mechanisms for reusable face coverings include interception and impaction, diffusion, and electrostatic attraction. Face covering development includes the identification of appropriate constituent fibers, yarn characteristics, and base fabric construction. Factors significantly affecting the filtration performance were electrostatic charge, particle size, porosity, layers, and finishes. Reusable face coverings offer several challenges including moisture management, breathing resistance factors, and balancing filtration with breathability. Efficacy of reusable face coverings in comparison to specialized non reusable masks in clinical trials has also been reviewed and discussed. Finally, the authors identified the use of certain finishes on fabrics as a major challenge to making reusable face coverings more effective and accessible to the public. This paper is expected to provide communities and research stakeholders with access to critical knowledge on the reusability of face coverings and their management during periods of global crisis.
... The present research focuses on improving the filtration efficiency of masks [53,[85][86][87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103]. Masks' protective performance largely depends on two significant factors: filtration efficiency and fit (facepiece leakage). ...
... Although there are many experimental methods for measuring the filtration efficiency of masks, there is no uniformly applied method in the current experimental research, owing to diverse research assumptions and objectives [85]. The current experimental methods and the factors affecting the filtration performance of masks are summarized in Table 2 [53,[86][87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103]. Due to the dependence of filtration efficiency on the size of particles, in general, the sizes of the aerosols used in experiments differ according to research purposes. ...
... It should be noted that a permeability index is also used to measure the filtration efficiency of a mask, and the sum of the permeability and filtration efficiency is 1. We reviewed some studies on the filtration efficiency of common fabric materials, medical masks, and N95 masks; examples of the relevant studies are provided here [27,30,53,86,87,90,92,93,101,[120][121][122][123]. Different researchers chose different aerosol sizes and types when studying the filtration efficiency of different types of masks. ...
Masks are essential and effective small protective devices used to protect the general public against infections such as COVID-19. However, available systematic reviews and summaries on the filtration performance of masks are lacking. Therefore, in order to investigate the filtration performance of masks, filtration mechanisms, mask characteristics, and the relationships between influencing factors and protective performance were first analyzed through mask evaluations. The summary of filtration mechanisms and mask characteristics provides readers with a clear and easy-to-understand theoretical cognition. Then, a detailed analysis of influencing factors and the relationships between the influencing factors and filtration performance is presented in. The influence of the aerosol size and type on filtration performance is nonlinear and nonconstant, and filtration efficiency decreases with an increase in the gas flow rate; moreover, fitness plays a decisive role in the protective effects of masks. It is recommended that the public should wear surgical masks to prevent COVID-19 infection in low-risk and non-densely populated areas. Future research should focus on fitness tests, and the formulation of standards should also be accelerated. This paper provides a systematic review that will be helpful for the design of masks and public health in the future.
... Any mask can decrease the number of microorganisms in some manner. Measurement of material filtration efficiencies can provide initial guidance on potential mask effectiveness for preventing outward and inward transmission (28). There is a need for additional researches and studies with a higher number of subjects, control groups and types of masks positioned in various conditions. ...
... Masks and respirators made of materials with larger pore sizes, such as cotton and synthetic fabric, will not be able to effectively filter viruses compared to those made of materials with smaller pore sizes. Masks and respirators made of or coated with water-resistant materials are more effective against large virus-laden respiratory droplets and fluid spills (15,28,29). Regarding non-medical masks made of different materials, giving general indications on the choice of materials and their composition is difficult because it is not possible to evaluate the efficiency for filtering different liquids or particles that can be emitted when breathing, sneezing or coughing in different environmental conditions. ...
Introduction. Protective equipment has become globally used to protect against respiratory infections in healthcare workers and sick patients. With the emergence of the SARS-CoV-2 virus and the global pandemic, the role of protective masks in reducing the transmission of the new virus has become the subject of much research. Although the protective mask has a significant role in reducing the transmission of infections, wearing it also has certain adverse effects. Aim. The aim of this review is to show the effectiveness of different types of protective masks in reducing the transmission of the SARS-CoV-2 virus, as well as the comparison of adverse effects when wearing protective masks. Methods. The method for analyzing the topic of the effectiveness of protective masks included reviews of papers found on the Google search engine, Medline database (via PubMed) and Hrcak. Included in the analysis are scientific papers with clinical trials or review papers, in English and Croatian, regardless of methodology, published since 2020. Included works include topics such as medical masks, respirators, cloth masks and their materials, effectiveness and importance of use, and adverse effects of wearing protective masks. A total of 2,110 articles, original and review papers were found, of which, after a detailed reading and analysis of several authors, 11 were selected that meet the eligibility criteria of this review paper.Results. There are filter half-masks with/without valve, surgical masks and hygienic or cloth masks. A surgical mask may provide better protection than a cloth mask, although this may depend on the layers and material the masks are made of. Respirator masks are somewhat more effective than surgical masks, but the difference turned out to be insignificant. The most common side effects of wearing masks for a long time are increased secretion of sputum, cough, dyspnea, difficulty when communicating, lack of closeness and feelings of insecurity. Conclusion. A face mask protects against infection and is associated with a reduced risk of infection. The habit of wearing a mask and the correct way of wearing it proved to be important factors in reducing the risk of infection.
... Davies et al. (2013) have found that traditional fabrics filter 49% to 86% of particles in the air up to 0.02 µm, while surgical masks up to 89% of these particles. Van der Sande et al. (2008) and Rengasamy et al. (2010) claimed that textile masks filter 3%-60% of the particles in the exhaled air. Insufficient research has been conducted to assess the effectiveness of wearing a mask over time, the comfort of the individual and possible side effects. ...
... In that study, the temperature of the microenvironment under the face masks was not measured, but the rise of the skin temperature of all participants was attributed to the temperature increment of the microenvironment under the mask. Another study (Rengasamy et al., 2010) reported that the temperature range of exhaled breath is 31.4-35.4 °C. ...
... The particulate matter filtering performance of cloth mask has been found to be lower than commercially available surgical masks and respirators (Rengasamy, Eimer & Shaffer, 2010;Shakya et al., 2017;Neupane et al., 2019). Davies et al. (2013) reported the filtering efficiency of two layered cloth mask made from commonly available fabrics using bacteriophase MS2 virus aerosol (~23 nm diameter) at a flow rate of 30 L min −1 . ...
... Commonly used cloth face masks have variable pore size and thread density depending on the nature of the fabrics (Fig. 2B and inset). The lower performance of cloth facemask (Rengasamy, Eimer & Shaffer, 2010;Shakya et al., 2017;Neupane et al., 2019;Konda et al., 2020) is also due to poor facial fitness and performance of material used. Studies have suggested to use tightly woven fabrics having high thread count and low porosity, such as quilting cotton and cotton sheets, to design relatively better performing cloth face masks (Konda et al., 2020;Neupane, Chaudhary & Sharma, 2020). ...
Respiratory protection devices such as face masks and respirators minimize the transmission of infectious diseases by providing a physical barrier to respiratory virus particles. The level of protection from a face mask and respirator depends on the nature of filter material, the size of infectious particle, breathing and environmental conditions, facial seal, and user compliance. The ongoing COVID‒19 pandemic has resulted in the global shortage of surgical face mask and respirator. In such a situation, significant global populations have either reused the single‒use face mask and respirator or used a substandard face mask fabricated from locally available materials. At the same time, researchers are actively exploring filter materials having novel functionalities such as antimicrobial, enhanced charge holding, and heat regulating properties to design potentially better face mask. In this work, we reviewed research papers and guidelines published primarily in last decade focusing on, (a) virus filtering efficiency, (b) impact of type of filter material on filtering efficiency, (c) emerging technologies in mask design, and (d) decontamination approaches. Finally, we provide future prospective on the need of novel filter materials and improved design.
... The MRDPS of cloth masks were higher than surgical masks and 3d medical masks, suggesting the discomfort level of cloth masks is greater. This may be due to the their thicker and less breathable material, less secure fit, potential for skin irritation, and higher tendency to slip down during use [41,42]. In addition, the discomfort level of masks among males are higher than females, suggesting that males are more sensitive to masks when doing light exercise. ...
Background
During the COVID-19 pandemic, masks proved to be an effective measure in preventing virus transmission. However, many people have reported discomfort and negative perceptions toward wearing masks, especially during physical activity. This study aims to evaluate the discomfort and adverse perceptions related to various mask types among young, healthy adults during light exercise, including sitting, stationary stepping, and stair climbing. The study also examines the extent to which masks influence physiological indicators of physical well-being.
Methods
The study was conducted in two stages at the campus hospital of Shantou University. In Stage 1, 20 healthy college students (10 males, 10 females) were recruited to identify the mask with the most substantial physiological and psychological impact among four types: KN95 respirators, surgical masks, cloth masks, and 3D medical masks. These specific types were chosen due to their widespread use and varying levels of filtration and breathability. In Stage 2, 14 healthy college students (7 males, 7 females) were included to examine the effects of the identified mask across various levels of physical exertion. Subjective perceptions were measured using the Mask-Related Discomfort and Perception Score (MRDPS), and physiological parameters such as body temperature, blood pressure, pulse rate, and vital capacity were recorded.
Results
The KN95 respirator and cloth mask were associated with the highest MRDPS, indicating significant discomfort among wearers (p < 0.05). The use of KN95 respirators had the largest impact on MRDPS during stair stepping (β = 10.357, 95% CI [5.755, 14.959]). Physiological parameters showed minor variations across different masks, with KN95 respirators significantly associated with reduced diastolic blood pressure (β=-7.806, 95% CI [-12.294, -3.318]) and pulse rate (β=-10.661, 95% CI [-18.896, -2.425]) in Stage 1. However, after controlling for exercise pace in Stage 2, wearing a KN95 respirator did not significantly affect these parameters.
Conclusions
KN95 respirators and cloth masks were found to cause the most discomfort during light physical activity, with males reporting higher discomfort levels than females. While these masks are associated with varying levels of perceived discomfort, their impact on physiological indicators is relatively modest. Future research should include larger and more diverse samples , continuous monitoring of physiological parameters during exercise, and exploration of the underlying mechanisms of gender differences in mask discomfort.
... Jung et al., (2014) have shown that different protocols have shown different values on the same parameters for the same fabric (Jung et al., 2014). An important observation is that fabric not originally intended for fabrication of face masks showed filtration efficiencies that varied greately over 40 to 90 per cent (Rengasamy et al., 2010). To be more universal, it is important to consider many factors before setting up standards for fabric used to make quick and do-it-yourself face masks as many fabrics may fail to pass if only one standard or one parameter is highlighted. ...
We report a quick, non-standard informative test method for assessing quality of fabrics intended for making facemasks. Highly efficient N95 facemasks masks are costly in Zambia (about US$ 1.20) hence need for cheap alternative facemask materials. Various materials were tested for filtration efficiency, breathability and effect of washing and ironing on these parameters. Filtration efficiency and breathability for monolayer-unwashed showed from highest to lowest; Java (98.00±1.40%,16754.7Pa/cm2), Telela (12.20±1.0%, 18.9 Pa/cm2); monolayer-washed; Cotton(200) pillow-case (87.1±0.1%,217Pa/cm2),Telela (16.5±0.1%,75.5Pa/cm2). Bilayer-unwashed; Java (99.7±0.1,25669.8Pa/cm2), Telela (59.5±3.5,47.2Pa/cm2), bilayer-washed and ironed; Java (99.7±0.1%,11603.8Pa/cm2), Telela (61.0±1.0%,113.2 Pa/cm2). The plain-inner with outer-honeycomb combination, was; grey (59.2±1.0%,150.9Pa/cm2) , black (52.8±0.8%,245.3Pa/cm2 ), yellow-khaki (99.3±0.3%, 490.6Pa/cm2 ) and stiffener (46.1±0.1%,18.9Pa/cm2). Results show that fabrics available are suitable for fabricating masks. Filtration efficiency increased while breathability remained within appreciable values compared with the reference. Washing and ironing had no significant effect on monolayers. Significance (p=0.0006) was shown when monolayer and bilayer fabrics were compared.
... Other research on the performance of fabrics and materials for making cloth face masks includes: Aydin et al., (2020); Chua et al., (2020); Clase et al., (2020); Davies et al., (2013); Jang and Kim (2015); Jung et al., (2014); Konda et al., (2020);MacIntyre et al., (2015); Mueller et al., (2020); Rengasamy et al., (2010); Rogak et al., (2020); Shakya et al., (2017); Tcharkhtchi et al., (2021); Teesing et al., (2020); van der Sande et al., (2008), Wilson et al., (2020); Zhao et al., (2020). ...
This study is based on a comprehensive bibliographic analysis of existing literature on PPE (Personal Protective Equipment), with a focus on face masks as a primary component. The aim of our research is to highlight the significant environmental impact of increased usage and improper disposal of PPE, leading to plastic pollution. In addition to consolidating existing knowledge on PPE, this paper explores the magnitude of the issue and reviews potential solutions, such as the development of biodegradable PPE, the use of cloth masks, effective waste management practices, and recycling and reusing methods.
... Cotton fabric can vary in physical properties, which may affect fabric efficiency. 25,26 Golanski et al. 17 tested nonwoven polypropylene, cotton, and Tyvek fabrics against graphite nanoparticles sized between 10 and 100 nm, and observed the highest penetration percentages were for cotton fabric and the lowest was for Tyvek; however, the authors, Golanski et al., focused only on a narrow size range and only one type of nanoparticle, which does not represent practical exposure scenarios in work environments. This study builds upon previous work by capturing a wide range of working conditions, environments, and exposure scenarios where workers may be exposed to different types of nanoparticles and determine the most protective lab coat fabrics for most situations. ...
... Studies have shown that the incorporation of electrostatic charges on filter media significantly improves the capture of fine particles. Notable research includes the work by Rengasamy et al. [31], which demonstrated that electrettreated filter media could achieve high filtration efficiency against nanoparticles. Understanding the electrostatic properties of respirator materials has practical implications for designing effective respiratory protection equipment. ...
The filtering mechanism of respirators involves static electricity and physical mechanisms, such as inertial impaction, interception, and diffusion. Static electricity is used to reduce pressure resistance, but electrostatic effects and the environmental variables that affect them are not well studied. Therefore, this study evaluated the contribution of static electricity to the filtration efficiency of respirators and the effects of changes in temperature and humidity on static electricity and the resulting filtration efficiency. Eight respirators from four manufacturers—four for workers (1st class respirators) and four for citizens (KF-94 respirators)—were selected, all of which met legal standards in Korea. The filtration efficiency and pressure drop were evaluated at baseline and after removing static electricity with isopropanol. To study the effects of humidity and temperature on the efficiency of the respirators, the respirators were exposed to 30, 50, and 98% humidity while the temperature was fixed at 25°C and to temperatures of −30, 25, and 70°C while the humidity was fixed at 50%. Static electricity was measured using a surface-potential meter, and the filtration efficiency was measured using NaCl and paraffin oil. When static electricity was removed from the 1st class and KF-94 respirators, the filtration efficiency decreased by 21.7% and 19.5%, respectively. Humidity affected the change in static electricity slightly more than temperature, but since not all static electricity was removed, the filtration efficiency was not affected greatly. The changes in static electricity and filtration efficiency due to humidity were significant, but this was because the standard deviation was small. Even under 98% humidity, the filtration efficiency was only 1–2% lower than that at 30% humidity and still met the 94% filtration efficiency criterion for respirators.
... Cloth masks: Despite their popularity, cloth masks present low filtration efficiency of aerosols, varying between 2-38% due to their large pores. Cloth masks composed of three or more layers present higher filtration ability [17]. After four wash and dry cycles, their filtration efficiency can lower by up to 20% [18]. ...
... The chemical nature of mask materials, e.g. natural, synthetic, or blended raw materials is another important parameter that is used in the evaluation of cloth masks 9,16,17,[20][21][22] . Cotton is the most common fiber type used in masks. ...
... 5 They make a barrier that can shield the user from fluid spray such as sneezing and hold the bacteria in liquid droplets from entering the user's nose or mouth. 6 Face masks have been broadly investigated in previous literature focusing on the material of the mask, 7-10 filtration efficiency, [11][12][13][14][15] design of the mask, 16,17 the utility of the mask, 6,[18][19][20][21][22] and its impact on the environment. [23][24][25][26] Disposable surgical masks, which are particularly used in clinical settings, have become widely used items among community members to either save themselves or others. ...
During the time of COVID-19, the use of face masks has become an essential control and prevention measure. The wide usage of disposable face masks has presented a great challenge to governments to face the impact of plastic waste on humans health and the environment. The quality of reusable face masks was assessed in previous research based on general measures such as the fabric, size fit, arrival time, price, and convenience, and based on more-specific measures related to the number of layers and the included filters. However, as the quality of reusable face masks includes several other dimensions, the general measures cannot be enough to ensure a comprehensive evaluation of these products during the COVID-19 outbreak. Nowadays, however, digital social media has provided venues and convenient tools for users to share their opinions, preferences, and experiences on the quality of reusable face masks. Considering reusable face masks, several types have been launched on online platforms to meet the increasing demand during COVID-19. The main goal of this study is to investigate how reusable face masks can be evaluated through online customers’ reviews. This study proposes a combination of qualitative (text mining) and quantitative (survey-based analysis) approaches to provide the researchers with a method of data analysis to inspect the most influential quality factors for the evaluation of reusable face masks. We performed a literature review on the previous works and also collected online customers’ reviews from Amazon.com to find the quality factors of reusable face masks. The review of previous literature on reusable face masks and the result of online reviews analysis indicated that several factors impact customers’ experiences, including filteration efficiency, fabric quality, breathability, design, functionality, environmental impact, comfort, easy to use, easy to clean, economic impact, donning/doffing, quality of seal, vision, communication and safety protection. The presented framework can be complementary to the existing evaluation research methods, which use the strengths of one method to overcome the shortcomings of the other.
... The guidelines for the care for pregnant women state that it is recommended to use, among other things, social distancing, compliance with the visiting schedule, and the use of isolation wards. Nasal masks can help reduce the spread of infection within the community (relative to non-surgical face masks, these devices have been shown to have extremely low filtering efficiency), minimize the shedding of respiratory droplets from infected individuals who may not be aware they are infected, and they do not yet show symptoms (16,17). ...
Objectives:
The aim of our research was to investigate the self-rated health status, health behaviour and hygiene habits of pregnant women, and to explore the influencing factors during the pandemic.
Methods:
The sample included 1,200 pregnant women who gave birth in the most progressive institutions of the three examined counties in Hungary; 839 questionnaires were returned, based on which the willingness to answer can be said to be 69.9%. After data cleaning, 640 questionnaires were added to the database. Descriptive statistical analyses and correlation tests were performed, during which we used the Pearson's chi-square test and Fisher's exact test.
Results:
Socio-demographic factors show a significant correlation with the perceived state of health and the degree of responsibility for health, however, the existence of a chronic disease does not affect either the self-assessed state of health or hygienic behaviour. Factors influencing hygienic behaviour include residence, education, assessed income, and gestational age. We found no correlation between health status and hygienic attitude.
Conclusions:
Our results draw attention to the fact that among pregnant women - especially pregnant women with low socioeconomic status - education about hygiene habits is of particular importance. Teamwork is needed in this area, which should start during the period of preparation for pregnancy, but at the latest in the early stages of pregnancy.
... Surgical masks have a wide range of filtration efficiencies (i.e., they vary in quality), with most showing 30% to 50% (Brosseau & Sietsema, 2020;Droegemeier, 2020). An aerosol permeation study showed that two of the five surgical masks studied had a penetration rate of 51% to 89% of aerosols (Rengasamy et al., 2010). In the early COVID pandemic, one study found that neither surgical nor cotton masks effectively filtered SARS-CoV-2 during coughs by infected patients, but this study was retracted (Bae et al., 2020). ...
Viral epidemics of acute respiratory infections pose a global threat. Influenza outbreaks occur almost every year. Specifically, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19), emerged in late 2019. This unprecedented event resulted in many countries requiring masks in public spaces to contain the spread of SARS-CoV-2. However, the early and previous systematic reviews of randomized controlled trials (RCTs) found that medical/surgical masks did not appear to reduce respiratory viral infections. Also, N95 respirators did not provide superior protection over surgical masks against viral infections or influenza-like infections among healthcare workers (HCWs), although N95 respirators theoretically provide better protection. This led to the recommendation not to wear facemasks as potential benefits are limited, and there is a risk of self-contamination if misused. However, with the ongoing spread of SARS-CoV-2, several health authorities suddenly shifted their recommendations and advised the general public to wear masks, with some governments even mandating it. By July 2023, the health-protective benefits of wearing facemasks are still conflicting, and debate over the idea of a mask mandate is ongoing. Therefore, this review aims to discuss ten reasons why face masks should not be imposed on the public again, which include the functional weaknesses of facemasks, lack of justification for the sudden change in the recommendations during the COVID-19 pandemic, the effectiveness of facemasks in the community and among HCWs based on the systematic reviews of the RCTs, their effectiveness based on the RCTs, the effectiveness of N95 respirators versus surgical masks in protecting from acute respiratory infection based on the systematic reviews, their potential harms, the poor quality of most masks used by the public, their misuse, the trajectory of the COVID-19 pandemic despite masking, and the importance of acknowledgment of the rights of people in wearing masks or not.
... It has been found that the blocking efficiency of fabrics for large droplets is comparable to that of a commercial medical mask, but the FE of nonelectrostatic cloth materials for small particles with a diameter about 0.3 μm is low and has close relation with fabric specifications (Konda et al. 2020;Aydin et al. 2020;Zhao et al. 2020;Mueller et al. 2020;Lima et al. 2020;Drewnick et al. 2020). Generally, the FE of various cloth masks is in the order of 10%-60% for polydisperse aerosols (d p = 20 nm-1000 nm), which is significantly lower than that of medical mask (FE = 60%-98%) (Rengasamy et al. 2010). For instance, the FE of 10 different materials including vacuum bag, superfine fiber cloth, double headscarves, pillowcase, cotton T-shirt was studied and the FE was between 10 and 75% (Pan et al. 2020). ...
The filtration efficiency of cloth masks for small harmful particles is usually low because of the large pore size of fabrics and the difficulty to choose appropriate fabric specifications. In this study, the polymers with antibiotic groups of quaternary amines were grafted onto cotton fabrics for achieving both satisfactory antibiotic and filtering performance. The results indicated that the pore size of the fabrics grafted with polymer brushes was significantly reduced and thus the filtration efficiency of polymer-grafted cotton fabrics can be increased to 81.5% ± 7.8% from 17.5% ± 2% of original fabrics under the tested level of 0.3 μm particles with 85 L/min flowing rate. The filtration efficiency of treated fabrics was comparable to the medical masks currently used in clinic. Moreover, the grafted fabrics also exhibited excellent antibacterial performance and washability. After 20 cycles of washing, they still had about 75.9% filtration efficiency and 99.9% bacterial inhibition rate for E. coli. This work could inspire the development of reusable and sustainable facemasks with effective personal protection for reducing the spread of COVID-19 and other infectious diseases.
Graphical abstract
... Both steps require proper training to be effective; Lipp et al. (2005) investigated the pattern of use and the protective effects of masks on wound infections using a questionnaire in two randomized studies. While the use of MNP was statistically beneficial in a smaller study (n = 200), the same recommendations were not valid when a larger cohort (n = 1250) was studied; Rengasamy (2010) looked at the protective effect of masks for everyday use made from different materials was tested against 20-1.000 nm particles with different velocities and compared to N95 masks. ...
The study looked at the acceptability of cloth nose masks produced during the outbreak of COVID 19 in a public University in Ghana. This study looked into staff consumers' views and experiences with the cloth nose mask produced by the Clothing Production Unit (CPU) of a public university in Ghana. The production quality, durability, comfortability, ease of care and acceptability of the cloth nose was assessed with the intent to use findings to guide future production. The study adopted the descriptive survey design. A self-developed structured questionnaire was used for detail data collection from one hundred (101) respondents who were purposively selected and conveniently reached. The findings generally presented high acceptance level for the cloth nose masks. Specifically, respondents rated sample two (46) and one (44) as the most preferred designs of the cloth nose mask. Also, respondents found the cloth nose masks quality in terms of production 92 (M=3.84), design (M=3.98), comfort of usage (M=3.77), durability (M=3.97), easiness in caring (M=3.95). The study concludes that the cloth nose masks produced by CPU meet consumer expectations and acceptance. This implies that if production is guided by improved practices the cloth nose masks would serve its intended purpose of controlling the spread of covid-19. Therefore, this survey recommends the adoption of the cloth nose masks to supplement other types recommended for use by World Health Organization (WHO) whilst maintaining and/or improving standards of production.
... 3M model 1860 -that a lack of strict requirement for proper charge neutralization is the only major factor preventing PSL aerosols from yielding PFE results on par with those of NaCl. This study has two main areas of focus: the characterization of the bipolar charge distribution on the aerosols used in testing, and the measurement of the PFE and DP of a range of materials common to community and occupational settings, including non-woven polypropylene (meltblown and spunbond), woven cotton, whole medical masks, and N95 respirators, supplementing the existing literature, e.g., (Rengasamy et al., 2010;Zangmeister et al., 2020;Drewnick et al., 2021;Rogak et al., 2021;Zhao et al., 2020;Crilley et al., 2021). Meltblown polypropylene is the primary filter material for both medical masks and respirators and exhibits low mechanical strength and good particle filtration efficiency (Sinha-Ray et al., 2014;Xiao et al., 2020). ...
... Knotting the mask loop makes it more comfortable to wear on the face. Microbes, viruses, aerosol, diesel exhaust, polystyrene, and microparticles have been used to measure the filtering capability of cloth masks [19]. The efficiency of masks in a controlled laboratory environment may not be feasible. ...
... Rogak et al. performed a similar study with micron based aerosols and found that many of the filter materials had a filtration of over 90% [21]. Rengasamy et al. evaluated five categories of common fabrics with both poly-and mono-dispersed aerosols ranging from 20 to 1000 nm [22]. They found that the materials had a wide penetration range (40-90%) against poly-dispersed NaCl aerosols and an even wider penetration range (9-98%) when discretely testing mono-disperse NaCl aerosols. ...
The onset of the 2019 novel coronavirus disease (COVID-19) led to a shortage of personal protective equipment (PPE), medical devices, and other medical supplies causing many stakeholders and the general public alike to turn to additive manufacturing (AM) as a stopgap when normally accessible devices were not available. However, without a method to test these AM constructs, there continued to be a disconnect between AM suppliers and the community's needs. The objective of this study was to characterize the pressure drop and leakage of four different publicly available AM face mask models with two filter material combinations, as well as to investigate the impact of frame modification techniques including the use of foam strips and hot-water face forming to improve fit when the masks are donned on manikin head forms. AM face mask frame designs were downloaded from public repositories during the early stages of the COVID-19 pandemic. AM face masks were fabricated and tested on manikin head forms within a custom chamber containing dry aerosolized NaCl. Pressure drops, particle penetration, and leakage were evaluated for various flow rates and NaCl concentrations. Results indicated that filter material combination and frame modification played a major role in the overall performance of the AM face masks studied. Filter material combinations showed improved performance when high filtration fabric was used, and the cross-sectional area of the fabric was increased. AM frame modifications appeared to improve AM face mask leakage performance by as much as 69.6%.
... Rengasamy (35) conducted laboratory tests with different materials: one-layer HMM with t-shirts, towels, scarfs and cotton. The particles went from 0.2 to 1 micron and they compared the efficiency with the N95. ...
... The SARS-CoV2 (COVID- 19) pandemic has led to people being required to wear protective face masks. In many countries, the requirement is limited to wearing masks indoorsin buildings and vehicles, but in some regions, the obligation temporarily and sporadically extends to all public places indoors and outdoors. ...
... Poor facial ft increases the particulate penetration level known as total inward leakage (TIL) [48,52] at diferent breathing frequencies [50] and particle penetration level decreases with increasing particle size [53,54]. Te TIL values were found to be low in SMs and N95 FFRs compared to CMs in our study and previous studies [55,56]. It is found that the efcacy of CMs widely varied from each other due to large pore size in CMs allowing particulates to pass easily, however, it performed well for larger particles >300 nm [42] and is believed to impede droplets and aerosols transmission [57]. ...
Inexpensive cloth masks are widely used to reduce particulate exposures, but their use became ubiquitous after the outbreak of COVID-19. A custom experimental setup (semiactive at 5.1 m/s airflow rate) was fabricated to examine the efficiency of different types of commercial facemasks collected randomly from street vendors. The sample (N = 27) including (n = 16) cloth masks (CMs), (n = 7) surgical masks (SMs), and (n = 4) N95 filtering facepiece respirators (FFRs), of which SMs and N95 FFRs taken as a standard for efficiency comparison were all tested against ambient aerosols (PM2.5 and PM10 μg/m3). The prototype cloth masks (PTCMs) (N = 5) design was tailored, and their performance was assessed and compared with that of standard commercial masks. The filtering efficiency tested against ambient coarse particulates (PM10) ranged from (5% to 34%) for CMs with an average of 16%, (37% to 46%) for SMs with an average of 42%, (59% to 72%) for PTCMs with an average of 65%, and (70% to 75%) for N95 FFRs with an average of 71%, whereas against fine particulates (PM2.5), efficacy ranged from (4% to 29%) for CMs with an average of 13%, (34% to 44%) for SMs with an average of 39%, (53% to 68%) for PTCMs with an average of 60%, and (68% to 73%) for N95 FFRs with an average of 70%, respectively. The efficiency followed the order N95 FFRs > PTCMs > SMs > CMs showing poor exposure reduction potential in CMs and high exposure reduction potential in N95 FFRs and PTCMs. Amendment in existing CMs using eco-friendly cotton fabric with better facial adherence can protect human health from exposure to fine particulates <2.5 μm and can reduce the risk of micro-plastic pollution caused by polypropylene (PP) facemasks.
... Previous studies [7] found that the surgical masks and N95 masks could reduce the penetration of exhaled droplet when coughing and talking by 50% and over 90%, respectively. As for cloth masks, they were usually made of one layer of cotton with the overall capture efficiency around 20%, which was lower than the surgical masks [8]. ...
COVID-19 has caused the global pandemic and had a serious impact on people's daily lives. The coronavirus mainly spreads between people through respiratory droplets produced from coughing and talking of an infected patient. To avoid the infection, the US Centers for Disease Control and Prevention (CDC) advised to wear face masks while maintaining a social distancing of 2 m. Can the social distancing be reduced if people wear masks? To answer this question, we measured the mass of inhaled droplets by a susceptible manikin wearing a mask with different social distances, which was produced by coughing and talking of an index "patient" (human subject) also wearing a mask. The experiment was conducted in an environmental chamber. We found that the social distancing could be reduced to 0.5 m when people wear face masks. In this case, the mass concentration of inhaled particles was less than two people without wearing masks and with a social distancing of 2 m, so that the risk of infection was lower. The results of this study would make business profitable with reduced social distancing in transportation, education and entertainment industries, which was beneficial for the reopening of the economy.
The aim of this paper is to report a unique method to make reusable washable fabric face mask that has good filtration efficiency and yet affordable using common fabric materials including the polypropylene filter available in the market to support the needs of universal masking. Part 1 study involved multiple combinations of common commercially available fabric materials to find the most filtration efficient combination for the purpose of making the reusable and washable fabric face mask. The filtration efficiency and breathing resistance of all prototypes were tested according to ASTM F2299/F2299M-03 standard using TSI 8130 High Flow Automated Filter Tester, and AFNOR SPEC S76-001:2020 using INSPEC Breathing Resistant Rig respectively in the National Institute of Occupational Safety and Health, Dust Mask Laboratory. The study found a unique combination of non-woven fusible interlinings fabric with melt blown polypropylene filter fabric to produce washable and reusable fabric mask that can sustain up to 50 normal household washing machine washes maintaining the filtration efficiency between 60–95% and breathing resistance below 4 milibar, which are acceptable to function as non-medical mask. Part 2 study involved field testing of the prototype face masks made from Part 1 study among randomly selected 764 school children in comparison arms. The experiment showed no increase in incidences of all-cause and sickness absenteeism using the prototype masks produced as compared to usual face masks at end of two months.
The efficacy of face masking for the public is not convincing to prevent the transmission of respiratory tract viruses such as SARS-CoV-2 when the criteria of evidence-based medicine are applied. This finding is mainly explained by the results from randomized-controlled trials (RCTs) when a high prevalence of the infection and a high compliance in mask wearing was assured. Throughout these studies no significant protective effect was observed. Observational studies with surgical masks describe a significant protective effect, but are prone to confounders such as physical distance. Respirators do not provide an additional health benefit compared to surgical or medical masks (RCTs). Community masks can even increase the risk of infection (RCTs). Based on the categories of evidence-based medicine, the efficacy results can best be categorized as conflicting evidence. Many relevant adverse events are described when masks are worn for hours such as dyspnea (12.2–52.8%), headache (3.9–73.4%), pruritus (0.0–60.0%), and skin reactions (0.0–85.0%). Their frequency is often higher with respirators. In future pandemics, masks should only be recommended or mandated for settings in which a clinically relevant health benefit can be expected, defined as the prevention of severe, critical or fatal disease, that clearly outweighs the expectable associated adverse reactions.
Purpose
Nanotechnology (NT) advancements in personal protective textiles (PPT) or personal protective equipment (PPE) have alleviated spread and transmission of this highly contagious viral disease, and enabled enhancement of PPE, thereby fortifying antiviral behavior.
Design/methodology/approach
Review of a series of state of the art research papers on the subject matter.
Findings
This paper expounds on novel nanotechnological advancements in polymeric textile composites, emerging applications and fight against COVID-19 pandemic.
Research limitations/implications
As a panacea to “public droplet prevention,” textiles have proven to be potentially effective as environmental droplet barriers (EDBs).
Practical implications
PPT in form of healthcare materials including surgical face masks (SFMs), gloves, goggles, respirators, gowns, uniforms, scrub-suits and other apparels play critical role in hindering the spreading of COVID-19 and other “oral-respiratory droplet contamination” both within and outside hospitals.
Social implications
When used as double-layers, textiles display effectiveness as SFMs or surgical-fabrics, which reduces droplet transmission to <10 cm, within circumference of ∼0.3%.
Originality/value
NT advancements in textiles through nanoparticles, and sensor integration within textile materials have enhanced versatile sensory capabilities, robotics, flame retardancy, self-cleaning, electrical conductivity, flexibility and comfort, thereby availing it for health, medical, sporting, advanced engineering, pharmaceuticals, aerospace, military, automobile, food and agricultural applications, and more. Therefore, this paper expounds on recently emerging trends in nanotechnological influence in textiles for engineering and fight against COVID-19 pandemic.
This narrative review and meta-analysis summarizes a broad evidence base on the benefits—and also the practicalities, disbenefits, harms and personal, sociocultural and environmental impacts—of masks and masking. Our synthesis of evidence from over 100 published reviews and selected primary studies, including re-analyzing contested meta-analyses of key clinical trials, produced seven key findings. First, there is strong and consistent evidence for airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory pathogens. Second, masks are, if correctly and consistently worn, effective in reducing transmission of respiratory diseases and show a dose-response effect. Third, respirators are significantly more effective than medical or cloth masks. Fourth, mask mandates are, overall, effective in reducing community transmission of respiratory pathogens. Fifth, masks are important sociocultural symbols; non-adherence to masking is sometimes linked to political and ideological beliefs and to widely circulated mis- or disinformation. Sixth, while there is much evidence that masks are not generally harmful to the general population, masking may be relatively contraindicated in individuals with certain medical conditions, who may require exemption. Furthermore, certain groups (notably D/deaf people) are disadvantaged when others are masked. Finally, there are risks to the environment from single-use masks and respirators. We propose an agenda for future research, including improved characterization of the situations in which masking should be recommended or mandated; attention to comfort and acceptability; generalized and disability-focused communication support in settings where masks are worn; and development and testing of novel materials and designs for improved filtration, breathability, and environmental impact.
The COVID-19 pandemic provides a unique opportunity to study science communication and, in particular, the transmission of consensus. In this study, we show how “science communicators,” writ large to include both mainstream science journalists and practiced conspiracy theorists, transform scientific evidence into two dueling consensuses using the effectiveness of masks as a case study. We do this by compiling one of the largest, hand-coded citation datasets of cross-medium science communication, derived from 5 million Twitter posts of people discussing masks. We find that science communicators selectively uplift certain published works while denigrating others to create bodies of evidence that support and oppose masks, respectively. Anti-mask communicators in particular often use selective and deceptive quotation of scientific work and criticize opposing science more than pro-mask communicators. Our findings have implications for scientists, science communicators, and scientific publishers, whose systems of sharing (and correcting) knowledge are highly vulnerable to what we term adversarial science communication.
“For the great doesn’t happen through impulse alone, and is a succession of little things that are brought together.” (van Gogh 1882)
“There is no need to reinvent the wheel for tires on the left side if the wheel already exists on the right.” (Helsel 2010)
Even a casual observer would have noticed that occupational hygienists have, over time, employed increasingly sophisticated statistics. While not a journal of biostatistics, the Annals of Work Exposures and Health has been a leader in the publication of novel applications of statistical methods to occupational hygiene data and questions. In honor of the 70th anniversary of the British Occupational Hygiene Society, this commentary seeks to describe some trends in statistical methods used in occupational hygiene exemplified by work in the Annals, highlighting some highly cited papers, as well as some that should have perhaps attracted more attention; we dare to predict what yet may come to pass, without replicating the sage advice offered by others (Riley et al. 2022). We apologize in advance for any important publications or developments that may have escaped our attention, and welcome letters that highlight articles that readers recognize as important to their learning, research, or practice.
Wearing face masks during pandemics is an important protective measure against the spreading of virus‐related infectious diseases. Nevertheless, the risk of indirect transmission of virus by handling masks is one of the earliest concerns. This problem can be minimized by supplementing the masks’ textile structure with virus protective coatings. Therefore, in this concept, suitable techniques for manufacturing virus protective filter media should be evaluated. In this study, nonwoven polyamide 6 (PA6) filter material is functionalized with negatively charged linear polyglycerol sulfate (LPGS) as a virus binding functional group. Two coating conditions are investigated in which the direct covalent coating with LPGS has emerged as the optimum coating method, showing no damage to the PA6 nanofiber structure. The uncoated PA6 and LPGS‐coated PA6 filter materials exhibited virus particle filtration efficiencies of 95% and 94% for airborne feline coronavirus, 98% and 86% for airborne equine herpesvirus 1(EHV‐1), respectively. However, the SARS‐CoV‐2 absorption assay in solution indicates that the LPGS coating reduces viral titres up to 71% when incubating with the LPGS‐coated PA6 filter media for one‐hour. Thus, such an effect is not seen for uncoated PA6 materials. These findings confirm the suitability of LPGS coating as a suitable platform for suppression the spreading of viruses in different pandemics.
Emerging infectious diseases that we are witnessing in the modern age are among the leading public health concerns. They most often occur in the form of epidemics or pandemics, and they have not been sufficiently researched. Owing to the current coronavirus disease 2019 (COVID-19) pandemic, the World Health Organization has published various recommendations to prevent the spread of this communicable disease, including a recommendation to wear protective facial masks. Therefore, this study aimed to determine the filtration effectiveness of bacteria, yeasts, and molds on three different commonly and commercially available masks used in children’s educational institutions. In addition, the bacterial content of indoor air bioaerosols was identified. The genera Staphylococcus and Micrococcus were dominant in all samples, whereas bacteria of the genera Bacillus, Acinetobacter, and Corynebacterium were identified at a significantly smaller number. Bacterial, yeast, and mold filtering effectiveness increased from the single-layer cloth mask, which proved to be the least effective, to the surgical mask, to the filtering facepiece type 2 (FFP2) mask. Furthermore, surveys are needed to study the effectiveness of protective measures.
This study experimentally measured the ventilation efficiency in road vehicles. Two air circulation methods, air conditioning and opening windows, were considered and their ventilation efficiencies were measured for a sedan and a cutaway bus. The ventilation efficiencies have been evaluated by measuring the aerosol concentration parameter at different locations inside the vehicle. For both vehicles, any of the ventilation scenarios significantly increased the air exchange rate. The best performance was shown when all windows were open in a moving vehicle. As an illustration of using the obtained measurements, respiratory infection probability was calculated using the Wells-Riley model. Any of the ventilation cases significantly decreased the infection risk. The ventilation efficiency and infection probability were highly dependent on the air circulation method and vehicle type.
The filtration of air has attracted increasing attention during recent waves of viral infection. This review considers published literature regarding the usage of cellulose-based materials in air filtration devices, including face masks. Theoretical aspects are reviewed, leading to models that can be used to predict the relationship between structural features of air filter media and the collection efficiency for different particle size classes of airborne particulates. Collection of particles can be understood in terms of an interception mechanism, which is especially important for particles smaller than about 300 nm, and a set of deterministic mechanisms, which become important for larger particles. The effective usage of cellulosic material in air filtration requires the application of technologies including pulp refining and chemical treatments with such additives as wet-strength agents and hydrophobic sizing agents. By utilization of high levels of refining, in combination with freeze drying and related approaches, there are opportunities to achieve high levels of interception of fine particles. A bulky layer incorporating nanofibrillated cellulose can be used in combination with a coarser ply to achieve needed strength in a filter medium. Results of recent research show a wide range of development opportunities for diverse air filter devices containing cellulose.
Background:
Viral epidemics or pandemics of acute respiratory infections (ARIs) pose a global threat. Examples are influenza (H1N1) caused by the H1N1pdm09 virus in 2009, severe acute respiratory syndrome (SARS) in 2003, and coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 in 2019. Antiviral drugs and vaccines may be insufficient to prevent their spread. This is an update of a Cochrane Review last published in 2020. We include results from studies from the current COVID-19 pandemic.
Objectives:
To assess the effectiveness of physical interventions to interrupt or reduce the spread of acute respiratory viruses.
Search methods:
We searched CENTRAL, PubMed, Embase, CINAHL, and two trials registers in October 2022, with backwards and forwards citation analysis on the new studies.
Selection criteria:
We included randomised controlled trials (RCTs) and cluster-RCTs investigating physical interventions (screening at entry ports, isolation, quarantine, physical distancing, personal protection, hand hygiene, face masks, glasses, and gargling) to prevent respiratory virus transmission. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methodological procedures.
Main results:
We included 11 new RCTs and cluster-RCTs (610,872 participants) in this update, bringing the total number of RCTs to 78. Six of the new trials were conducted during the COVID-19 pandemic; two from Mexico, and one each from Denmark, Bangladesh, England, and Norway. We identified four ongoing studies, of which one is completed, but unreported, evaluating masks concurrent with the COVID-19 pandemic. Many studies were conducted during non-epidemic influenza periods. Several were conducted during the 2009 H1N1 influenza pandemic, and others in epidemic influenza seasons up to 2016. Therefore, many studies were conducted in the context of lower respiratory viral circulation and transmission compared to COVID-19. The included studies were conducted in heterogeneous settings, ranging from suburban schools to hospital wards in high-income countries; crowded inner city settings in low-income countries; and an immigrant neighbourhood in a high-income country. Adherence with interventions was low in many studies. The risk of bias for the RCTs and cluster-RCTs was mostly high or unclear. Medical/surgical masks compared to no masks We included 12 trials (10 cluster-RCTs) comparing medical/surgical masks versus no masks to prevent the spread of viral respiratory illness (two trials with healthcare workers and 10 in the community). Wearing masks in the community probably makes little or no difference to the outcome of influenza-like illness (ILI)/COVID-19 like illness compared to not wearing masks (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.84 to 1.09; 9 trials, 276,917 participants; moderate-certainty evidence. Wearing masks in the community probably makes little or no difference to the outcome of laboratory-confirmed influenza/SARS-CoV-2 compared to not wearing masks (RR 1.01, 95% CI 0.72 to 1.42; 6 trials, 13,919 participants; moderate-certainty evidence). Harms were rarely measured and poorly reported (very low-certainty evidence). N95/P2 respirators compared to medical/surgical masks We pooled trials comparing N95/P2 respirators with medical/surgical masks (four in healthcare settings and one in a household setting). We are very uncertain on the effects of N95/P2 respirators compared with medical/surgical masks on the outcome of clinical respiratory illness (RR 0.70, 95% CI 0.45 to 1.10; 3 trials, 7779 participants; very low-certainty evidence). N95/P2 respirators compared with medical/surgical masks may be effective for ILI (RR 0.82, 95% CI 0.66 to 1.03; 5 trials, 8407 participants; low-certainty evidence). Evidence is limited by imprecision and heterogeneity for these subjective outcomes. The use of a N95/P2 respirators compared to medical/surgical masks probably makes little or no difference for the objective and more precise outcome of laboratory-confirmed influenza infection (RR 1.10, 95% CI 0.90 to 1.34; 5 trials, 8407 participants; moderate-certainty evidence). Restricting pooling to healthcare workers made no difference to the overall findings. Harms were poorly measured and reported, but discomfort wearing medical/surgical masks or N95/P2 respirators was mentioned in several studies (very low-certainty evidence). One previously reported ongoing RCT has now been published and observed that medical/surgical masks were non-inferior to N95 respirators in a large study of 1009 healthcare workers in four countries providing direct care to COVID-19 patients. Hand hygiene compared to control Nineteen trials compared hand hygiene interventions with controls with sufficient data to include in meta-analyses. Settings included schools, childcare centres and homes. Comparing hand hygiene interventions with controls (i.e. no intervention), there was a 14% relative reduction in the number of people with ARIs in the hand hygiene group (RR 0.86, 95% CI 0.81 to 0.90; 9 trials, 52,105 participants; moderate-certainty evidence), suggesting a probable benefit. In absolute terms this benefit would result in a reduction from 380 events per 1000 people to 327 per 1000 people (95% CI 308 to 342). When considering the more strictly defined outcomes of ILI and laboratory-confirmed influenza, the estimates of effect for ILI (RR 0.94, 95% CI 0.81 to 1.09; 11 trials, 34,503 participants; low-certainty evidence), and laboratory-confirmed influenza (RR 0.91, 95% CI 0.63 to 1.30; 8 trials, 8332 participants; low-certainty evidence), suggest the intervention made little or no difference. We pooled 19 trials (71, 210 participants) for the composite outcome of ARI or ILI or influenza, with each study only contributing once and the most comprehensive outcome reported. Pooled data showed that hand hygiene may be beneficial with an 11% relative reduction of respiratory illness (RR 0.89, 95% CI 0.83 to 0.94; low-certainty evidence), but with high heterogeneity. In absolute terms this benefit would result in a reduction from 200 events per 1000 people to 178 per 1000 people (95% CI 166 to 188). Few trials measured and reported harms (very low-certainty evidence). We found no RCTs on gowns and gloves, face shields, or screening at entry ports.
Authors' conclusions:
The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions. There were additional RCTs during the pandemic related to physical interventions but a relative paucity given the importance of the question of masking and its relative effectiveness and the concomitant measures of mask adherence which would be highly relevant to the measurement of effectiveness, especially in the elderly and in young children. There is uncertainty about the effects of face masks. The low to moderate certainty of evidence means our confidence in the effect estimate is limited, and that the true effect may be different from the observed estimate of the effect. The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection. Hand hygiene is likely to modestly reduce the burden of respiratory illness, and although this effect was also present when ILI and laboratory-confirmed influenza were analysed separately, it was not found to be a significant difference for the latter two outcomes. Harms associated with physical interventions were under-investigated. There is a need for large, well-designed RCTs addressing the effectiveness of many of these interventions in multiple settings and populations, as well as the impact of adherence on effectiveness, especially in those most at risk of ARIs.
Recent studies suggest that humans exhale fine particles during tidal breathing but little is known of their composition, particularly during infection.
We conducted a study of influenza infected patients to characterize influenza virus and particle concentrations in their exhaled breath. Patients presenting with influenza-like-illness, confirmed influenza A or B virus by rapid test, and onset within 3 days were recruited at three clinics in Hong Kong, China. We collected exhaled breath from each subject onto Teflon filters and measured exhaled particle concentrations using an optical particle counter. Filters were analyzed for influenza A and B viruses by quantitative polymerase chain reaction (qPCR). Twelve out of thirteen rapid test positive patients provided exhaled breath filter samples (7 subjects infected with influenza B virus and 5 subjects infected with influenza A virus). We detected influenza virus RNA in the exhaled breath of 4 (33%) subjects--three (60%) of the five patients infected with influenza A virus and one (14%) of the seven infected with influenza B virus. Exhaled influenza virus RNA generation rates ranged from <3.2 to 20 influenza virus RNA particles per minute. Over 87% of particles exhaled were under 1 microm in diameter.
These findings regarding influenza virus RNA suggest that influenza virus may be contained in fine particles generated during tidal breathing, and add to the body of literature suggesting that fine particle aerosols may play a role in influenza transmission.
Considerable controversy exists with regard to whether influenza virus and respiratory syncytial virus (RSV) are spread by the inhalation of infectious airborne particles and about the importance of this route, compared with droplet or contact transmission.
Airborne particles were collected in an urgent care clinic with use of stationary and personal aerosol samplers. The amounts of airborne influenza A, influenza B, and RSV RNA were determined using real-time quantitative polymerase chain reaction. Health care workers and patients participating in the study were tested for influenza.
Seventeen percent of the stationary samplers contained influenza A RNA, 1% contained influenza B RNA, and 32% contained RSV RNA. Nineteen percent of the personal samplers contained influenza A RNA, none contained influenza B RNA, and 38% contained RSV RNA. The number of samplers containing influenza RNA correlated well with the number and location of patients with influenza (r= 0.77). Forty-two percent of the influenza A RNA was in particles < or = 4.1 microm in aerodynamic diameter, and 9% of the RSV RNA was in particles < or = 4.1 microm.
Airborne particles containing influenza and RSV RNA were detected throughout a health care facility. The particles were small enough to remain airborne for an extended time and to be inhaled deeply into the respiratory tract. These results support the possibility that influenza and RSV can be transmitted by the airborne route and suggest that further investigation of the potential of these particles to transmit infection is warranted.
To review systematically the evidence of effectiveness of physical interventions to interrupt or reduce the spread of respiratory viruses.
Cochrane Library, Medline, OldMedline, Embase, and CINAHL, without restrictions on language or publication. Data selection Studies of any intervention to prevent the transmission of respiratory viruses (isolation, quarantine, social distancing, barriers, personal protection, and hygiene). A search of study designs included randomised trials, cohort, case-control, crossover, before and after, and time series studies. After scanning of the titles, abstracts and full text articles as a first filter, a standardised form was used to assess the eligibility of the remainder. Risk of bias of randomised studies was assessed for generation of the allocation sequence, allocation concealment, blinding, and follow-up. Non-randomised studies were assessed for the presence of potential confounders and classified as being at low, medium, or high risk of bias.
58 papers of 59 studies were included. The quality of the studies was poor for all four randomised controlled trials and most cluster randomised controlled trials; the observational studies were of mixed quality. Meta-analysis of six case-control studies suggested that physical measures are highly effective in preventing the spread of severe acute respiratory syndrome: handwashing more than 10 times daily (odds ratio 0.45, 95% confidence interval 0.36 to 0.57; number needed to treat=4, 95% confidence interval 3.65 to 5.52), wearing masks (0.32, 0.25 to 0.40; NNT=6, 4.54 to 8.03), wearing N95 masks (0.09, 0.03 to 0.30; NNT=3, 2.37 to 4.06), wearing gloves (0.43, 0.29 to 0.65; NNT=5, 4.15 to 15.41), wearing gowns (0.23, 0.14 to 0.37; NNT=5, 3.37 to 7.12), and handwashing, masks, gloves, and gowns combined (0.09, 0.02 to 0.35; NNT=3, 2.66 to 4.97). The combination was also effective in interrupting the spread of influenza within households. The highest quality cluster randomised trials suggested that spread of respiratory viruses can be prevented by hygienic measures in younger children and within households. Evidence that the more uncomfortable and expensive N95 masks were superior to simple surgical masks was limited, but they caused skin irritation. The incremental effect of adding virucidals or antiseptics to normal handwashing to reduce respiratory disease remains uncertain. Global measures, such as screening at entry ports, were not properly evaluated. Evidence was limited for social distancing being effective, especially if related to risk of exposure-that is, the higher the risk the longer the distancing period.
Routine long term implementation of some of the measures to interrupt or reduce the spread of respiratory viruses might be difficult. However, many simple and low cost interventions reduce the transmission of epidemic respiratory viruses. More resources should be invested into studying which physical interventions are the most effective, flexible, and cost effective means of minimising the impact of acute respiratory tract infections.
Size-fractionated aerosol particles were collected in a hospital emergency department to test for airborne influenza virus.
Using real-time polymerase chain reaction, we confirmed the presence of airborne influenza virus and found that 53% of detectable
influenza virus particles were within the respirable aerosol fraction. Our results provide evidence that influenza virus may
spread through the airborne route.
Humans commonly exhale aerosols comprised of small droplets of airway-lining fluid during normal breathing. These “exhaled bioaerosols” may carry airborne pathogens and thereby magnify the spread of certain infectious diseases, such as influenza, tuberculosis, and severe acute respiratory syndrome. We hypothesize that, by altering lung airway surface properties through an inhaled nontoxic aerosol, we might substantially diminish the number of exhaled bioaerosol droplets and thereby provide a simple means to potentially mitigate the spread of airborne infectious disease independently of the identity of the airborne pathogen or the nature of any specific therapy. We find that some normal human subjects expire many more bioaerosol particles than other individuals during quiet breathing and therefore bear the burden of production of exhaled bioaerosols. Administering nebulized isotonic saline to these “high-producer” individuals diminishes the number of exhaled bioaerosol particles expired by 72.10 ± 8.19% for up to 6 h. In vitro and in vivo experiments with saline and surfactants suggest that the mechanism of action of the nebulized saline relates to modification of the physical properties of the airway-lining fluid, notably surface tension.
• drug delivery
• lung
• infectious disease
• influenza
To systematically review evidence for the effectiveness of physical interventions to interrupt or reduce the spread of respiratory viruses.
Search strategy of the Cochrane Library, Medline, OldMedline, Embase, and CINAHL, without language restriction, for any intervention to prevent transmission of respiratory viruses (isolation, quarantine, social distancing, barriers, personal protection, and hygiene). Study designs were randomised trials, cohort studies, case-control studies, and controlled before and after studies.
Of 2300 titles scanned 138 full papers were retrieved, including 49 papers of 51 studies. Study quality was poor for the three randomised controlled trials and most of the cluster randomised controlled trials; the observational studies were of mixed quality. Heterogeneity precluded meta-analysis of most data except that from six case-control studies. The highest quality cluster randomised trials suggest that the spread of respiratory viruses into the community can be prevented by intervening with hygienic measures aimed at younger children. Meta-analysis of six case-control studies suggests that physical measures are highly effective in preventing the spread of SARS: handwashing more than 10 times daily (odds ratio 0.45, 95% confidence interval 0.36 to 0.57; number needed to treat=4, 95% confidence interval 3.65 to 5.52); wearing masks (0.32, 0.25 to 0.40; NNT=6, 4.54 to 8.03); wearing N95 masks (0.09, 0.03 to 0.30; NNT=3, 2.37 to 4.06); wearing gloves (0.43, 0.29 to 0.65; NNT=5, 4.15 to 15.41); wearing gowns (0.23, 0.14 to 0.37; NNT=5, 3.37 to 7.12); and handwashing, masks, gloves, and gowns combined (0.09, 0.02 to 0.35; NNT=3, 2.66 to 4.97). The incremental effect of adding virucidals or antiseptics to normal handwashing to decrease the spread of respiratory disease remains uncertain. The lack of proper evaluation of global measures such as screening at entry ports and social distancing prevent firm conclusions being drawn.
Routine long term implementation of some physical measures to interrupt or reduce the spread of respiratory viruses might be difficult but many simple and low cost interventions could be useful in reducing the spread.
This work investigated the size distribution of the droplet nuclei and coughed droplets by test subjects. The size distributions of droplet nuclei coughed by test subjects were determined with an aerodynamic particle sizer (APS) and scanning mobility particle sizer (SMPS) system (system 1). Coughed droplets were only sampled with the APS system (system 2). Two different schemes were employed in system 2. Furthermore, the size distribution of coughed droplets of different ages and gender was investigated to identify the effects of age and gender on droplet size distribution. Results indicated the total average size distribution of the droplet nuclei was 0.58-5.42 microm, and 82% of droplet nuclei centered in 0.74-2.12 microm. The entire average size distribution of the coughed droplets was 0.62-15.9 microm, and the average mode size was 8.35 microm. The size distribution of the coughed droplets was multimodal. The size distribution of coughed droplets showed three peaks at approximately 1 microm, 2 microm, and 8 microm. These analytical findings indicate that variation for average droplet size among the three age groups was insignificant (p > 0.1). Moreover, the variation in average droplet size between males and females was also insignificant (p > 0.1). Also, the variation in droplet concentration between males and females was significant (p > 0.1). Droplet nuclei concentrations from male subjects were considerably higher than that from females. Comparison of the droplet concentrations for subjects in different age groups demonstrated that subjects in the 30-50-year age group have the largest droplet concentrations.
Governments are preparing for a potential influenza pandemic. Therefore they need data to assess the possible impact of interventions. Face-masks worn by the general population could be an accessible and affordable intervention, if effective when worn under routine circumstances.
We assessed transmission reduction potential provided by personal respirators, surgical masks and home-made masks when worn during a variety of activities by healthy volunteers and a simulated patient.
All types of masks reduced aerosol exposure, relatively stable over time, unaffected by duration of wear or type of activity, but with a high degree of individual variation. Personal respirators were more efficient than surgical masks, which were more efficient than home-made masks. Regardless of mask type, children were less well protected. Outward protection (mask wearing by a mechanical head) was less effective than inward protection (mask wearing by healthy volunteers).
Any type of general mask use is likely to decrease viral exposure and infection risk on a population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection. Masks worn by patients may not offer as great a degree of protection against aerosol transmission.
Dust masks are often confused with filtering facepiece respirators (FFR) but are not approved by NIOSH for respiratory protection against particulate exposure. This study reports the filtration performance of commercially available dust masks against submicron particles and discusses the relevance of these findings toward the filtration of nanoparticles. Seven different models of dust masks from local home improvement/hardware stores were challenged with submicron NaCl particles, and initial percentage penetration and resistance levels were measured using two test procedures. A polydisperse aerosol test (PAT) method, similar to the "worst case" conditions used in the NIOSH particulate respirator certification test protocol was used. A monodisperse aerosol test (MAT) method, which utilizes eleven different particle sizes in the range of 20-400 nm, were also used for particle penetration measurements at 30 and 85 L/min flow rates using the TSI 3160. Dust masks were designated as category low-, medium- and high-penetration dust masks based on penetration levels of <5%, 5-25% and >25%, respectively. Data collected using the PAT and the MAT methods showed <5% initial penetration levels for low-penetration dust masks, which is similar to the NIOSH-approved class-95 filtering facepiece respirators. Average penetration levels for medium- and high-penetration dust masks were between 8.9-24.2% and 74.5-96.9%, respectively. Penetration levels of MPPS particles from the MAT correlated with penetration levels from the PAT. Monodisperse MPPS penetration levels from MAT and penetration levels from PAT showed poor correlation with resistance values and no correlation with cost. The results of this study show that dust masks frequently do not provide filtration performance equivalent to that of NIOSH certified devices. Users of dust masks should be cautioned against using them for protection against particulates in the nano- or ultrafine size ranges.
Ashortage of NIOSH-approved respirators is predicted during an influenza pandemic and other infectious disease outbreaks. Healthcare workers may use surgical masks instead of respirators due to non-availability and for economical reasons. This study investigated the filtration performance of surgical masks for a wide size range of submicron particles including the sizes of many viruses. Five models of FDA-cleared surgical masks were tested for room air particle penetrations at constant and cyclic flow conditions. Penetrations of polydisperse NaCl aerosols (75±20 nm, count median diameter), monodisperse NaCl aerosols (20-400 nm range) and particles in the 20-1000 nm range were measured at 30 and 85 liters/min. Filtration performance of surgical masks varied widely for room air particles at constant flow and correlated with the penetration levels measured under cyclic flow conditions. Room air particle penetration levels were comparable to polydisperse and monodisperse aerosol penetrations at 30 and 85 liters/minute. Filtration performance of FDA-cleared surgical masks varied widely for room air particles, and monodisperse and polydisperse aerosols. The results suggest that not all FDA-cleared surgical masks will provide similar levels of protection to wearers against infectious aerosols in the size range of many viruses.
The efficacy of readily available materials, such as cotton fabric, toweling, and a single-use respirator, for providing emergency respiratory protection was evaluated by determining the filtration efficiency as a function of particle size over the range of 0.4 to 5 µm diameter and performance against a reactive water soluble (I2) and unreactive vapor (CH3I). At a reasonable design face velocity (1.5 cm/s), the respirator mask used at double thickness could reduce particle concentrations a factor of 30 or more throughout the particle range tested, and a wetted towel four layers thick could provide a factor of five. Dry fabrics were ineffective in removing iodine vapor, but wetted sheeting or toweling reduced concentration by a factor of ten or more under design conditions, 1.5 cm/s face velocity and 50 Pa pressure drop (0.2 inches of water). The fabrics provided a statistically insignificant reduction in methyl iodide. In practice, any leaks around the seal to the face would lessen the protection offered by such materials. The effectiveness factor approach proved useful in comparing filter performance under different conditions.
The National Institute for Occupational Safety and Health (NIOSH) and European Norms (ENs) employ different test protocols for evaluation of air-purifying particulate respirators commonly referred to as filtering facepiece respirators (FFR). The relative performance of the NIOSH-approved and EN-certified 'Conformité Européen' (CE)-marked FFR is not well studied. NIOSH requires a minimum of 95 and 99.97% efficiencies for N95 and P100 FFR, respectively; meanwhile, the EN requires 94 and 99% efficiencies for FFRs, class P2 (FFP2) and class P3 (FFP3), respectively. To better understand the filtration performance of NIOSH- and CE-marked FFRs, initial penetration levels of N95, P100, FFP2 and FFP3 respirators were measured using a series of polydisperse and monodisperse aerosol test methods and compared. Initial penetration levels of polydisperse NaCl aerosols [mass median diameter (MMD) of 238 nm] were measured using a method similar to the NIOSH respirator certification test method. Monodisperse aerosol penetrations were measured using silver particles for 4-30 nm and NaCl particles for 20-400 nm ranges. Two models for each FFR type were selected and five samples from each model were tested against charge neutralized aerosol particles at 85 l min(-1) flow rate. Penetrations from the 238 nm MMD polydisperse aerosol test were <1% for N95 and FFP2 models and <0.03% for P100 and FFP3 models. Monodisperse aerosol penetration levels showed that the most penetrating particle size (MPPS) was in the 30-60 nm range for all models of FFRs tested in the study. Percentage penetrations at the MPPS were <4.28, <2.22, <0.009 and <0.164 for the N95, FFP2, P100 and FFP3 respirator models, respectively. The MPPS obtained for all four FFR types suggested particle capturing by electrostatic mechanism. Liquid isopropanol treatment of FFRs shifted the MPPS to 200-300 nm and dramatically increased polydisperse as well as monodisperse aerosol penetrations of all four FFR types indicating that all the four FFR types share filtration characteristics of electret filters. Electrostatic charge removal from all four FFR types also increased penetration levels of 400-1000 nm range particles. Particle penetration data obtained in this study showed that the eight models of NIOSH-approved N95 and P100 and CE-marked FFP2 and FFP3 respirators used in this study provided expected levels of laboratory filtration performance against nanoparticles.
Measurements were made of the number concentrations of particles in exhaled breath under various conditions of exercise. A laser light scattering particle spectrometer was used to count particles exhaled by test subjects wearing respirators in a challenge environment of clean, dry air. Precautions were taken to ensure that particles were not generated by the the respirators and that no extraneous water or other particles were produced in the humid exhaled air. The number of particles detected in exhaled air varied over a range from less than 0.1 to about 4 particles per cm3 depending upon the test subject and his activity. Subjects at rest exhaled the lowest concentration of particles, whereas exercises producing a faster respiration rate caused increased exhalation of particles. Exhaled particle concentrations can limit the usefulness of nondiscriminating, ambient challenge aerosols for the fit testing of highly protective respirators.
In areas where respirators are not routinely used, emergencies (such as fires) may occur in which protection from airborne particles is necessary. The following readily available materials were tested on a manikin connected to a breathing simulator to determine the fraction of an approximately 2-micron diameter aerosol that would leak around the seal between the materials and the manikin's face: cotton/polyester shirt material, cotton handkerchief material, toweling (a wash cloth), a surgical mask (Johnson & Johnson Co., Model HRI 8137), and a NIOSH-approved disposable face mask (3M Corp., Model #8710). The leakage tests were done to supplement the measurements of penetration through the materials reported previously. Leakage fractions were determined by comparing the penetration of the same aerosol for the materials held to the face versus being fully taped to the face. At a breathing rate of 37 liters per minute, mean leakages for the materials ranged from 0.0 percent to 63 percent, depending on the material. Mean penetrations exclusive of leakage ranged from 0.6 percent to 39 percent. Use of nylon hosiery material ("panty hose") to hold the handkerchief material or the disposable face mask to the face was found to be very effective in preventing leakage. Such a combination could be expected to reduce leakage around the handkerchief to about 10 percent or less in practice, and around the mask to less than one percent, which suggests the adaptation and use of such an approach for industrial hygiene.
Droplets carried in exhaled breath may carry microorganisms capable of transmitting disease over both short and long distances. The size distribution of such droplets will influence the type of organisms that may be carried as well as strategies for controlling airborne infection. The aim of this study was to characterize the size distribution of droplets exhaled by healthy individuals. Exhaled droplets from human subjects performing four respiratory actions (mouth breathing, nose breathing, coughing, talking) were measured by both an optical particle counter (OPC) and an analytical transmission electron microscope (AEM). The OPC indicated a preponderance of particles less than 1 mu, although larger particles were also found. Measurements with the AEM confirmed the existence of larger sized droplets in the exhaled breath. In general, coughing produced the largest droplet concentrations and nose breathing the least, although considerable intersubject variability was observed.
Eighteen variations of eight household and personal items were evaluated
with use of human subjects to determine their potential utilization as emergency
respiratory protection expedients in the event of a radiological or biological
attack. Five variations of these items have a filtration efficiency greater
than 85%. They are manss cotton handkerchief folded to a thickness of 16 layers,
folded to a thickness of 8 layers, or placed over the mouth in a crumpled state;
a commercially available toilet papers when used in a thickness of three sheets;
a bath towel, when folded in two layers. Howevers the high resistance of the
hankerchief when folded to give 16 layers and when crumpled limits the usage of
these two variations to short intervals of time. In order to determine if wet
items were superior to dry items, five of the cloth materials were evaluated
after beingsaturated with water and subsequently hand-wrung. The most efficient
of these items was found to be the bath towel (70.2%). This result is less than
that obtained for seven dry items. Four of the five wet items exhibited
extremely high resistandce to breathing. Therefore, the use of wet iterts as
respiratory protective expedients appears impractical. (auth)
In this survey of infectious diseases consultants, 90% reported that their health care facilities have plans in place to address
severe acute respiratory syndrome (SARS). Some plan elements exceed current recommendations, whereas others are less stringent.
Resource issues associated with airborne isolation and respirators were reported. Sixty-one percent of the respondents expressed
some concern about their facility's preparation and capacity for managing patients with SARS. Recent draft guidance on SARS
preparedness from the Centers for Disease Control and Prevention may help address some of these issues.
The current understanding of airborne pathogen spread in relation to the new methods of suppressing exhaled bioaerosols using safe surface-active materials, such as isotonic saline, is reviewed here. We discuss the physics of bioaerosol generation in the lungs, what is currently known about the relationship between expired bioaerosols and airborne infectious disease and current methods of airborne infectious disease containment. We conclude by reviewing recent experiments that suggest the delivery of isotonic saline can significantly diminish exhaled aerosol--generated from airway lining fluid in the course of natural breathing. We also discuss these implications in relation to airborne infectious disease control.
Surgical masks have been used since the early 1900s to minimize infection of surgical wounds from wearer-generated bacteria. There is ongoing debate, however, whether surgical masks can meet the expectations of respiratory protection devices. The goal of this study was to evaluate the filter performance and facial fit of a sample of surgical masks.
Filter penetration was measured for at least 3 replicates of 9 surgical masks using monodisperse latex sphere aerosols (0.895, 2.0, and 3.1 microm) at 6 L/min and 0.075-microm sodium chloride particles at 84 L/min. Facial fit was measured on 20 subjects for the 5 masks with lowest particle penetration, using both qualitative and quantitative fit tests.
Masks typically used in dental settings collected particles with significantly lower efficiency than those typically used in hospital settings. All subjects failed the unassisted qualitative fit test on the first exercise (normal breathing). Eighteen subjects failed the assisted qualitative fit tests; 60% failed on the first exercise. Quantitative fit factors ranged from 2.5 to 9.6.
None of these surgical masks exhibited adequate filter performance and facial fit characteristics to be considered respiratory protection devices.
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