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Filtration Efficiency and Pressure Drop Across Materials Tested with Aerosols of Bacillus atrophaeus and Bacteriophage MS2 (30 L/min) a
Source publication
This study examined homemade masks as an alternative to commercial face masks.
Several household materials were evaluated for the capacity to block bacterial and viral aerosols. Twenty-one healthy volunteers made their own face masks from cotton t-shirts; the masks were then tested for fit. The number of microorganisms isolated from coughs of healt...
Contexts in source publication
Context 1
... this study, common household materials (see Table 1) were challenged with high concentrations of bacterial and viral aerosols to assess their filtration efficiencies. Surgical masks have been considered the type of mask most likely to be used by the general public, and these were used as a control. ...
Context 2
... the materials tested showed some capability to block the microbial aerosol challenges. In general, the filtration efficiency for bacteriophage MS2 was 10% lower than for B atrophaeus (Table 1). The surgical mask had the highest filtration efficiency when challenged with bacteriophage MS2, followed by the vacuum cleaner bag, but the bag's stiffness and thickness created a high pressure drop across the material, rendering it unsuitable for a face mask. ...
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Citations
... The demand for personal protective equipment, including polymer filters, has surged in recent times. Research has demonstrated the efficacy of these polymer filter materials, with studies identifying materials capable of filtering over 95% of virus-containing particles [23,24]. However, while these studies focus on the overall filtration efficiency of materials in ideal settings, they often overlook the individual properties of each mask layer. ...
The selection of an appropriate fabric for technical applications, such as protective masks, hinges on a thorough understanding of the fabric's physical and mechanical properties. This study addresses the challenge of selecting the optimal material structure for the upper layer of a protective mask, aiming to ensure adequate breathability while providing effective filtration against airborne particles and contaminants. We assessed and compared the physical-mechanical properties of five polymer spun-bond nonwoven fabrics from different suppliers. Our comprehensive evaluation included , as follows: a visual inspection; light permeability analysis; mass and thickness measurements ; elongation and tensile strength tests; breathing resistance assessments; and filter penetration tests with paraffin oil. The results revealed significant variations in performance among the samples, with one fabric consistently outperforming the others across multiple parameters. Notably, this top-performing fabric met or exceeded the EN 149:2001+A1:2009 standard for breathing resistance and filtration efficiency and, in combination with additional filter layers, met the requirements or exceeded class FFP2 (filtering face piece). This study underscores the importance of meticulous material selection and quality control in optimizing PPE (personal protective equipment) performance and user safety, providing valuable insights for mask manufacturers and healthcare professionals.
... Masks can be of various types i.e. homemade face masks, surgical masks, N95 (N99, N100) and FFP's (FFP1, FFP2 & FFP3) respirators. While respirators are considered gold standard for preventing of COVID-19, there is evidence that even homemade masks can be considered as last resort and better than no protection when it comes to preventing of droplet infection 36 . Surgical masks on the contrary to belief, are not designed to protect the wearer. ...
The spread of COVID-19 has posed significant challenges for dentistry all around the globe and is causing a huge financial unsustainability for all healthcare workers. Due to the unique characteristics of dental practices, dental health care providers are at a higher risk of contracting COVID-19. The route of spread can be direct transmission such as cough, sneeze, aerosol producing procedures, inhalation of droplets and through direct contact transmission with symptomatic as well as asymptomatic patients. The potentially affected hospitals and dental practices require strict and efficient infection control protocols. With the evolving situation, due to COVID-19, routine dental cross infection control measures are not enough to safeguard dental care providers and seekers. Hence, these extraordinary times call for extraordinary measures. Modification and enhancement of the existing protocols is required e.g. use of Personal Protective Equipment in all dental practices should be implemented in routine dentistry, adaptation in the sterilization and disinfection techniques is inevitable and it may have to be incorporated permanently in to our daily practices. In this current pandemic, the digital dentistry has emerged as a new trend and it needs to be a part of our curriculum in undergraduate as well as postgraduate courses and it also needs to become part of our routine practices even after this virus ends.
... Previous studies of fitted filtration efficiency for medical and non-medical masks have been limited by very small sample sizes and incomplete descriptions of the masks. For cloth masks, our data (47-55%) are in keeping with the higher end of reported fitted filtration efficiencies: 27% (3-ply cotton on earloops, 0.02-3µm particles, 1 participant, 4 replicates) 5 ; 28% (2-ply, 3ply and 4-ply polyester, cotton and poly-cotton masks on earloops, 0.1µm particles; 3-4 participants, 1 replicate) 50 ; 50% (2-ply cotton T-shirt fabric, on overhead elastic ties, <0.1µm particles, 21 participants, 1 replicate) [51][52][53] ; 52% (head attachments and material not reported, 5 designs including 1-ply and bandana fabric, <0.1µm particles, 3 participants, 1 replicate). 42 This . ...
Importance
Masks reduce transmission of SARS-CoV2 and other respiratory pathogens. Comparative studies of the fitted filtration efficiency of different types of masks of are few.
Objective
To describe the fitted filtration efficiency against small aerosols (0.02 – 1 µm) of medical and non-medical masks and respirators when worn, and how this is affected by user modifications (hacks) and by overmasking with a cloth mask.
Design
We tested a 2-layer woven-cotton cloth mask of a consensus design, ASTM-certified level 1 and level 3 masks, a non-certified mask, KF94s, KN95s, an N95 and a CaN99.
Setting
Closed rooms with ambient particles supplemented by salt particles.
Participants
12 total participants; 21 – 55 years, 68% female, 77% white, NIOSH 1 to 10.
Main Outcome and Measure
Using standard methods and a PortaCount 8038, we counted 0.02–1µm particles inside and outside masks and respirators, expressing results as the percentage filtered by each mask. We also studied level 1 and level 3 masks with earguards, scrub caps, the knot-and-tuck method, and the effects of braces or overmasking with a cloth mask.
Results
Filtration efficiency for the cloth mask was 47-55%, for level 1 masks 52-60%, for level 3 masks 60-77%. A non-certified KN95 look-alike, two KF94s, and three KN95s filtered 57-77%, and the N95 and CaN99 97-98% without fit testing. External braces and overmasking with a well-fitting cloth mask increased filtration, but earguards, scrub caps, and the knot-and-tuck method did not.
Limitations
Limited number of masks of each type sampled; no adjustment for multiple comparisons.
Conclusions and Relevance
Well-fitting 2-layer cotton masks filter in the same range as level 1 masks when worn: around 50%. Level 3 masks and KN95s/KF94s filter around 70%. External braces or overmasking with a cloth-mask-on-ties produced filtration around 90%. Only N95s and CaN99s, both of which have overhead elastic, performed close to the occupational health and safety standards for fit tested PPE (>99%), filtering at 97-99%, without fit testing. These findings inform public health messaging about relative protection from aerosols from different mask types and increase understanding of findings of studies of implementation of masks and respirators.
Key Points
Question: How well do medical and non-medical masks filter aerosols when worn?
Findings: Well-fitting 2-layer cotton masks, and level 1 medical masks were similar, both filtering around 50% of aerosols. Level 3 masks and KN95/KF94s were similar, filtering around 70%. N95s and CaN99s, without formal fit testing, filtered 97-98%.
Meaning: Level 1 medical masks were not better than the well-fitting 2-layer cotton masks we tested. KN95/KF94s are not as efficient, when worn, as N95s and CaN99s. Overmasking and the use of external braces improve filtration: these are potentially useful strategies when N95s are not available.
Abstract Figure
... Our study found that 88.9% of participants considered cloth masks to be ineffective. This finding is consistent with empirical studies [34][35][36] demonstrating that cloth masks are one-third less effective than medical masks. As research findings suggest that cloth masks play a limited role in reducing the risk of COVID-19 virus exposure, these findings underscore the importance of training regarding differential effectiveness and appropriate face mask use [37]. ...
Background: Nurses are essential members of the healthcare workforce and were among the first-line carers for patients in community and hospital settings during the COVID-19 pandemic. As a result, they were at a heightened risk of infection, resulting in several reported deaths among nursing staff. Several preventive measures were adopted to contain the spread of the COVID-19 virus. This study aims to explore the knowledge, attitudes, and practices (KAP) of nurses regarding hand hygiene, mask wearing, and social distancing measures in healthcare settings in Barbados during the COVID-19 pandemic. Method: An online survey of nurses working in public hospitals and polyclinics (public primary care clinics) in Barbados from March 2021 to December 2021 was conducted. A nonsystematic convenience sampling method was employed to recruit nurses who were readily available and willing to participate. A questionnaire captured the sociodemographic information and knowledge and practices related to hand hygiene, the use of face masks, and social distancing. Each correct response received one mark. Overall knowledge scores were categorized as poor (<60%), average (60–80%), or good (>80–100%). Results: Of the 192 participants, the majority were female (82.8%) and had >5 years of experience (82%). The findings revealed that 45.8% had poor knowledge of hand hygiene, and that the knowledge of 43.8% of respondents was average. Multivariable logistic regression showed that, after adjustment for age and gender, registered nurses had 2.1 times increased odds (95% confidence interval 1.0, 4.2) of having good knowledge compared to other nursing categories. Regarding mask wearing, 53.6% of nurses had average knowledge, and 27.1% had good knowledge. Multivariable logistic regression showed that, after adjustment for age and gender, registered nurses had 3.3 times increased odds (95% confidence interval 1.5, 7.4) of having good knowledge compared to nursing assistants. A total of 68.6% of respondents followed the correct steps of handwashing every time, and 98.3% wore a mask in public places. More than half of the nurses (51.2%) kept a safe distance from others to avoid spreading SARS-CoV-2; one-third were in a crowded place(s) in the past three months, and 55.8% usually followed guidelines for social isolation as recommended by the WHO. Conclusions: The study identified knowledge deficiencies related to hand hygiene and wearing masks among nurses. It is imperative to provide additional training on infection control measures.
... 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.
... Policymakers encourage the use of cotton-made masks as personal protective equipment. Non-surgical masks are regarded as nonstandardized and not meant for usage by health care professionals in contrast to medical masks [9]. The effectiveness of face masks against various airborne transmission is best studied in controlled environments, such as when worn in hospitals by qualified personnel [10]. ...
... Where V is the cabin volume, κ is the cabin air exchange rate. θ is the mask permeability coefficient and ranges from 0 to 1; 0 represents complete isolation of the pathogen by the mask, while the filtration efficiency of a standard surgical mask for an aerosol containing viruses is approximately 60% [28]. Considering the potential for some passengers to experience air leakage when wearing masks, θ can be set at 50% to eliminate the impact of this factor [10]. ...
Civil aviation transport is an important source of global respiratory disease spread due to the closely-spaced environment. In order to reduce the probability of infection of passengers, an improved Wells-Riley model for cabin passenger risk assessment have been given in this work, the cabin ventilation and passenger nose and mouth orientation were considered. The model’s effectiveness has been verified with published data. Finally, how the load factor and use of an empty seat scheme are associated with the number of infected people was assessed. The results demonstrated that the number of infected people positively correlates with the passenger load factor, and the most suitable load factor can be determined by controlling the final number of infected people with the condition of the epidemic situation in the departure city. Additionally, infection risk was found to be lower among passengers in window seats than in those in aisle seats and middle seats, and keeping empty seats in the middle or aisle could reduce the cabin average probability of infection by up to 37.47%. Using the model developed here, airlines can determine the optimal load factor threshold and seating arrangement strategy to improve economic benefits and reduce the probability of passenger infection.
... (8) However, in this study, a handmade two-layered cotton tissue mask was most commonly used, despite studies indicating that it was not an effective filter for respiratory droplets. (9)(10)(11) Despite the physical barriers to free breathing, in this study, masks were not associated with any clinical manifestations. The slight decrease in PSO 2 observed in young adult men had no clinical relevance according to the volunteers, who complained only of minor ear discomfort due to short elastic bands and allergic reactions to the mask and elastic band material. ...
Objective
The World Health Organization and Centers for Disease Control and Prevention recommend the use of face masks in public. This study aimed to evaluate the effects of face masks on pulse rate and partial blood oxygen saturation in patients without cardiorespiratory disorders.
Methods
A total of 150 volunteers of both sexes were divided into three groups (n=50) according to age (children, young adults, and older adults). The partial blood oxygen saturation and pulse rate were measured for each volunteer using a digital oximeter while wearing a facial mask and remaining at rest. The masks were removed for two minutes, and partial blood oxygen saturation and pulse rate were remeasured. The materials and types of masks used were recorded. The t -test for paired samples was used to compare the mean values obtained before and after removing the masks.
Results
The most frequently used mask was a two-layered cloth (64.7%). A decrease in pulse rate was observed after removing the face mask in males, particularly in children (p=0.006) and young adults (p=0.034). Partial blood oxygen saturation levels increased in young adult males after mask removal (p=0.01).
Conclusion
The two-layer cotton tissue face masks are associated with a higher pulse rate and reduced arterial blood oxygen saturation without associated clinical disorders, mainly in adult men with a lower tolerance to breathing and ear discomfort.
Facial masks; Heart rate; Oxygen saturation; Respiration; SARS-CoV-2; Coronavirus infections; Age factors
... During pandemics caused by respiratory pathogens, especially when efficacious pharmaceutical treatments are unavailable, many experts recommend universal masking in public [11,12]. However, overwhelming demand for respiratory protection can severely strain commercial supplies [13,14], requiring some front-line workers and others to use improvised or homemade protection [15,16]. A major challenge is to develop an improvised mask that both front-line workers as well as non-experts can produce for ad-hoc respiratory protection. ...
... 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]. ...
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.
... Of course, this type of mask only filters air breathed in, and does not reduce virus transmission from an infected wearer to others. Testing in laboratory settings conducted at the University of Cambridge showed that a 100% cotton t-shirt showed a mean filtration efficiency of 70.7% for Bacillus atrophaeus compared to 96.4% for a surgical mask 19 . It was concluded that homemade face coverings should not be recommended to reduce transmission of infectious aerosols unless it was a last resort. ...
... It was concluded that homemade face coverings should not be recommended to reduce transmission of infectious aerosols unless it was a last resort. It can only provide effective protection if paired with other methods of virus suppression such as isolation of the infected, social distancing, immunisation and hand hygiene 19 . Whilst materials such as cotton have been shown to offer limited protection 20 , a key reason for their popularity is the comfort, and apparent breathability afforded to the wearer 21 . ...
... Substrate materials. Cotton is commonly used as a material for face masks and coverings 17,82 due to its availability, comfort, breathability, and moderate filtration performance 19,82 . Two non-woven 4-layer swab variants of size 5 × 5 cm, made of cotton, were purchased online from JFA medical Ltd in the UK. ...
The novel coronavirus pandemic (COVID-19) has necessitated a global increase in the use of face masks to limit the airborne spread of the virus. The global demand for personal protective equipment has at times led to shortages of face masks for the public, therefore makeshift masks have become commonplace. The severe acute respiratory syndrome caused by coronavirus-2 (SARS-CoV-2) has a spherical particle size of ~97 nm. However, the airborne transmission of this virus requires the expulsion of droplets, typically ~0.6–500 µm in diameter (by coughing, sneezing, breathing, and talking). In this paper, we propose a face covering that has been designed to effectively capture SARS-CoV-2 whilst providing uncompromised comfort and breathability for the wearer. Herein, we describe a material approach that uses amorphous silica microspheres attached to cotton fibres to capture bioaerosols, including SARS CoV-2. This has been demonstrated for the capture of aerosolised proteins (cytochrome c, myoglobin, ubiquitin, bovine serum albumin) and aerosolised inactivated SARS CoV-2, showing average filtration efficiencies of ~93% with minimal impact on breathability.
