Aerosol filtration efficiency of household materials for homemade face masks: Influence of material properties, particle size, particle electrical charge, face velocity, and leaks

doi:10.1080/02786826.2020.1817846

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Aerosol filtration efficiency of household materials for homemade face masks: Influence of material properties, particle size, particle electrical charge, face velocity, and leaks

Journal Article•DOI•

Aerosol filtration efficiency of household materials for homemade face masks: Influence of material properties, particle size, particle electrical charge, face velocity, and leaks

Frank Drewnick¹, Julia Pikmann¹, Friederike Fachinger¹, Lasse Moormann¹, Fiona Sprang¹, Stephan Borrmann² - Show less +2 more•Institutions (2)

Max Planck Society¹, University of Mainz²

02 Jan 2021-Aerosol Science and Technology (Taylor & Francis)-Vol. 55, Iss: 1, pp 63-79

TL;DR: Particle-size dependent filtration efficiencies (FE; dp) as mentioned in this paper were used in the COVID-19 pandemic caused by the SARS-CoV-2 virus.

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Abstract: As a consequence of the COVID-19 pandemic caused by the SARS-CoV-2 virus, the widespread daily use of face masks is promoted worldwide. Particle-size dependent filtration efficiencies (FE; dp = 30 ...

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Journal Article•DOI•

Airborne transmission of respiratory viruses.

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Chia C. Wang¹, Chia C. Wang², Kimberly A. Prather¹, Josué Sznitman³, Jose L. Jimenez³, Jose L. Jimenez⁴, Seema S. Lakdawala⁵, Zeynep Tufekci⁶, Linsey C. Marr², Linsey C. Marr⁷ - Show less +6 more•Institutions (7)

University of California, San Diego¹, National Sun Yat-sen University², Technion – Israel Institute of Technology³, University of Colorado Boulder⁴, University of Pittsburgh⁵, University of North Carolina at Chapel Hill⁶, Virginia Tech⁷

27 Aug 2021-Science

TL;DR: In this article, the authors discuss current evidence regarding the transmission of respiratory viruses by aerosols-how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission.

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Abstract: The COVID-19 pandemic has revealed critical knowledge gaps in our understanding of and a need to update the traditional view of transmission pathways for respiratory viruses. The long-standing definitions of droplet and airborne transmission do not account for the mechanisms by which virus-laden respiratory droplets and aerosols travel through the air and lead to infection. In this Review, we discuss current evidence regarding the transmission of respiratory viruses by aerosols-how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission. Improved understanding of aerosol transmission brought about by studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection requires a reevaluation of the major transmission pathways for other respiratory viruses, which will allow better-informed controls to reduce airborne transmission.

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492 citations

Journal Article•DOI•

Face masks effectively limit the probability of SARS-CoV-2 transmission.

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Yafang Cheng¹, Nan Ma², Christian Witt³, Steffen Rapp⁴, Philipp S. Wild⁴, Meinrat O. Andreae⁵, Meinrat O. Andreae⁶, Meinrat O. Andreae¹, Ulrich Pöschl¹, Hang Su⁷ - Show less +6 more•Institutions (7)

Max Planck Society¹, Jinan University², Charité³, University of Mainz⁴, King Saud University⁵, University of California, San Diego⁶, Fudan University⁷

25 Jun 2021-Science

TL;DR: In this article, the authors show that variations in mask efficacy can be explained by different regimes of virus abundance and related to population-average infection probability and reproduction number, and that most environments and contacts are under conditions of low virus abundance (virus-limited) where surgical masks are effective at preventing virus spread.

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Abstract: Airborne transmission by droplets and aerosols is important for the spread of viruses. Face masks are a well-established preventive measure, but their effectiveness for mitigating SARS-CoV-2 transmission is still under debate. We show that variations in mask efficacy can be explained by different regimes of virus abundance and related to population-average infection probability and reproduction number. For SARS-CoV-2, the viral load of infectious individuals can vary by orders of magnitude. We find that most environments and contacts are under conditions of low virus abundance (virus-limited) where surgical masks are effective at preventing virus spread. More advanced masks and other protective equipment are required in potentially virus-rich indoor environments including medical centers and hospitals. Masks are particularly effective in combination with other preventive measures like ventilation and distancing.

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176 citations

Journal Article•DOI•

Model Calculations of Aerosol Transmission and Infection Risk of COVID-19 in Indoor Environments.

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Jos Lelieveld¹, Jos Lelieveld², Frank Helleis², Stephan Borrmann², Yafang Cheng², Frank Drewnick², Gerald H. Haug², Thomas Klimach², Jean Sciare¹, Jean Sciare², Hang Su², Ulrich Pöschl² - Show less +8 more•Institutions (2)

The Cyprus Institute¹, Max Planck Society²

03 Nov 2020-International Journal of Environmental Research and Public Health

TL;DR: It is suggested that aerosols from highly infective subjects can effectively transmit COVID-19 in indoor environments, and active room ventilation and the ubiquitous wearing of face masks may reduce the individual infection risk by a factor of five to ten, similar to high-volume, high-efficiency particulate air (HEPA) filtering.

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Abstract: The role of aerosolized SARS-CoV-2 viruses in airborne transmission of COVID-19 has been debated. The aerosols are transmitted through breathing and vocalization by infectious subjects. Some authors state that this represents the dominant route of spreading, while others dismiss the option. Here we present an adjustable algorithm to estimate the infection risk for different indoor environments, constrained by published data of human aerosol emissions, SARS-CoV-2 viral loads, infective dose and other parameters. We evaluate typical indoor settings such as an office, a classroom, choir practice, and a reception/party. Our results suggest that aerosols from highly infective subjects can effectively transmit COVID-19 in indoor environments. This “highly infective” category represents approximately 20% of the patients who tested positive for SARS-CoV-2. We find that “super infective” subjects, representing the top 5–10% of subjects with a positive test, plus an unknown fraction of less—but still highly infective, high aerosol-emitting subjects—may cause COVID-19 clusters (>10 infections). In general, active room ventilation and the ubiquitous wearing of face masks (i.e., by all subjects) may reduce the individual infection risk by a factor of five to ten, similar to high-volume, high-efficiency particulate air (HEPA) filtering. A particularly effective mitigation measure is the use of high-quality masks, which can drastically reduce the indoor infection risk through aerosols.

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156 citations

Journal Article•DOI•

Covid-19 has redefined airborne transmission.

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Julian W. Tang¹, Linsey C. Marr², Yuguo Li³, Stephanie J. Dancer⁴•Institutions (4)

University of Leicester¹, Virginia Tech², University of Hong Kong³, Edinburgh Napier University⁴

14 Apr 2021-BMJ

121 citations

Posted Content•DOI•

Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield

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Jin Pan¹, Charbel Harb¹, Weinan Leng¹, Linsey C. Marr¹•Institutions (1)

Virginia Tech¹

10 Mar 2021-Aerosol Science and Technology

TL;DR: A three-layer mask consisting of outer layers of a flexible, tightly woven fabric and an inner layer consisting of a material designed to filter out particles is recommended, which should produce an overall efficiency of >70% at the most penetrating particle size and >90% for particles 1 m and larger if the mask fits well.

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Abstract: We evaluated the effectiveness of 11 face coverings for material filtration efficiency, inward protection efficiency on a manikin, and outward protection efficiency on a manikin. At the most penetr...

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108 citations

Cites background or methods from "Aerosol filtration efficiency of ho..."

...The number of layers 319 (Drewnick et al. 2020), the properties of the fibers including diameter and electrostatic charges 320 (Konda et al. 2020; Ou et al. 2020; Podgórski, Bałazy and Gradoń 2006; Zangmeister et al. 2020), 321 and the material composition (Zangmeister et al. 2020; Zhao et al.…...
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...472 Based on these results and other studies (Drewnick et al. 2020), we recommend a three-layer mask 473 consisting of two outer layers of a very flexible, tightly woven fabric and an inner layer consisting 474 of a material designed to filter out particles....
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...Other studies 257 have also reported that vacuum bags have high filtration efficiencies (Drewnick et al. 2020; 258 Zangmeister et al. 2020), whereas the performance of microfiber varies depending on the 259 manufacturer and fabric structure (Drewnick et al. 2020; Zhao et al. 2020)....
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...We did not test masks constructed of multiple layers of fabric, 470 as prior work has shown that overall filtration efficiency is readily predicted by combining 471 individual layers in series (Drewnick et al. 2020)....
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...The filtration efficiencies of 44 materials and medical masks, challenged with 67 sodium chloride (NaCl) particles of diameter 0.03–0.25 µm, ranged from <10% for polyurethane 68 foam to nearly 100% for a vacuum cleaner bag (Drewnick et al. 2020)....
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References

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Open Access

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Atmospheric chemistry and physics: from air pollution to climate change.

[...]

John H. Seinfeld, Spyros N. Pandis

01 Jan 2006

TL;DR: In this article, the authors present a model for the chemistry of the Troposphere of the atmosphere and describe the properties of the Atmospheric Aqueous phase of single aerosol particles.

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Abstract: 1 The Atmosphere. 2 Atmospheric Trace Constituents. 3 Chemical Kinetics. 4 Atmospheric Radiation and Photochemistry. 5 Chemistry of the Stratosphere. 6 Chemistry of the Troposphere. 7 Chemistry of the Atmospheric Aqueous Phase. 8 Properties of the Atmospheric Aerosol. 9 Dynamics of Single Aerosol Particles. 10 Thermodynamics of Aerosols. 11 Nucleation. 12 Mass Transfer Aspects of Atmospheric Chemistry. 13 Dynamics of Aerosol Populations. 14 Organic Atmospheric Aerosols. 15 Interaction of Aerosols with Radiation. 16 Meteorology of the Local Scale. 17 Cloud Physics. 18 Atmospheric Diffusion. 19 Dry Deposition. 20 Wet Deposition. 21 General Circulation of the Atmosphere. 22 Global Cycles: Sulfur and Carbon. 23 Climate and Chemical Composition of the Atmosphere. 24 Aerosols and Climate. 25 Atmospheric Chemical Transport Models. 26 Statistical Models.

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11,157 citations

Journal Article•DOI•

Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1.

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Neeltje van Doremalen¹, Trenton Bushmaker¹, Dylan H. Morris², Myndi G. Holbrook¹, Amandine Gamble³, Brandi N. Williamson¹, Azaibi Tamin⁴, Jennifer L Harcourt⁴, Natalie J. Thornburg⁴, Susan I. Gerber⁴, James O. Lloyd-Smith³, Emmie de Wit, Vincent J. Munster - Show less +9 more•Institutions (4)

National Institutes of Health¹, Princeton University², University of California, Los Angeles³, Centers for Disease Control and Prevention⁴

17 Mar 2020-The New England Journal of Medicine

TL;DR: Aerosol and Surface Stability of SARS-CoV-2 In this research letter, investigators report on the stability of Sars-CoVs and the viability of the two virus under experimental conditions.

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Abstract: Aerosol and Surface Stability of SARS-CoV-2 In this research letter, investigators report on the stability of SARS-CoV-2 and SARS-CoV-1 under experimental conditions. The viability of the two virus...

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7,412 citations

"Aerosol filtration efficiency of ho..." refers background in this paper

...…as well as various studies, e.g., showing transmission over distances >1–2m (Li et al. 2020), however, suggest that also other routes of transmission such as airborne transmission may play an important role (Hadei et al. 2020; van Doremalen et al. 2020; Morawska and Milton 2020; Zhang et al. 2020)....
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...This is known to be the case for pathogens causing pulmonary tuberculosis, measles, or chickenpox (WHO 2014), however, also for SARSCoV-2 viability in aerosol particles over more than an hour has been demonstrated (van Doremalen et al. 2020)....
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Journal Article•DOI•

Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles

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Günter Oberdörster¹, Eva Oberdörster, Jan Oberdörster•Institutions (1)

University of Rochester¹

22 Mar 2005-Environmental Health Perspectives

TL;DR: Results of older bio-kinetic studies with NSPs and newer epidemiologic and toxicologic studies with airborne ultrafine particles can be viewed as the basis for the expanding field of nanotoxicology, which can be defined as safety evaluation of engineered nanostructures and nanodevices.

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Abstract: Although humans have been exposed to airborne nanosized particles (NSPs; < 100 nm) throughout their evolutionary stages, such exposure has increased dramatically over the last century due to anthropogenic sources. The rapidly developing field of nanotechnology is likely to become yet another source through inhalation, ingestion, skin uptake, and injection of engineered nanomaterials. Information about safety and potential hazards is urgently needed. Results of older bio-kinetic studies with NSPs and newer epidemiologic and toxicologic studies with airborne ultrafine particles can be viewed as the basis for the expanding field of nanotoxicology, which can be defined as safety evaluation of engineered nanostructures and nanodevices. Collectively, some emerging concepts of nanotoxicology can be identified from the results of these studies. When inhaled, specific sizes of NSPs are efficiently deposited by diffusional mechanisms in all regions of the respiratory tract. The small size facilitates uptake into cells and transcytosis across epithelial and endothelial cells into the blood and lymph circulation to reach potentially sensitive target sites such as bone marrow, lymph nodes, spleen, and heart. Access to the central nervous system and ganglia via translocation along axons and dendrites of neurons has also been observed. NSPs penetrating the skin distribute via uptake into lymphatic channels. Endocytosis and biokinetics are largely dependent on NSP surface chemistry (coating) and in vivo surface modifications. The greater surface area per mass compared with larger-sized particles of the same chemistry renders NSPs more active biologically. This activity includes a potential for inflammatory and pro-oxidant, but also antioxidant, activity, which can explain early findings showing mixed results in terms of toxicity of NSPs to environmentally relevant species. Evidence of mitochondrial distribution and oxidative stress response after NSP endocytosis points to a need for basic research on their interactions with subcellular structures. Additional considerations for assessing safety of engineered NSPs include careful selections of appropriate and relevant doses/concentrations, the likelihood of increased effects in a compromised organism, and also the benefits of possible desirable effects. An interdisciplinary team approach (e.g., toxicology, materials science, medicine, molecular biology, and bioinformatics, to name a few) is mandatory for nanotoxicology research to arrive at an appropriate risk assessment.

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7,092 citations

"Aerosol filtration efficiency of ho..." refers methods in this paper

...…methods like European standard EN 14683, or filtering facepiece respirators (FFR), certified for filtration efficiency and seal leakage rate according to test procedures like European standard EN 149 (e.g., FFP2), which protect the wearer (Lee, Grinshpun, and Reponen 2008; Oberg and Brosseau 2008)....
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Book•

Aerosol Technology : Properties, Behavior, and Measurement of Airborne Particles

[...]

William C. Hinds

27 Jul 1982

TL;DR: Properties of Gases Uniform Particle Motion Particle size Statistics Straight-Line Acceleration and Curvilinear Particle motion Adhesion of Particles Brownian Motion and Diffusion Thermal and Radiometric Forces Filtration Sampling and Measurement of Concentration Respiratory Deposition Coagulation Condensation and Evaporation Atmospheric Aerosols Electrical Properties Optical Properties Bulk Motion of aerosols Dust Explosions Bioaerosols Microscopic measurement of Particle Size Production of Test aerosols Appendices Index Index

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Abstract: Properties of Gases Uniform Particle Motion Particle Size Statistics Straight-Line Acceleration and Curvilinear Particle Motion Adhesion of Particles Brownian Motion and Diffusion Thermal and Radiometric Forces Filtration Sampling and Measurement of Concentration Respiratory Deposition Coagulation Condensation and Evaporation Atmospheric Aerosols Electrical Properties Optical Properties Bulk Motion of Aerosols Dust Explosions Bioaerosols Microscopic Measurement of Particle Size Production of Test Aerosols Appendices Index

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5,208 citations

"Aerosol filtration efficiency of ho..." refers background or methods or result in this paper

...In airborne (or aerosol) transmission, the virus is transported via droplet nuclei or smaller aerosol particles (dp 5 mm) suspended in air (WHO 2014), which can stay suspended in air over extended periods of time (Hinds 1999)....
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...Particle removal from an airstream is caused by five physical mechanisms: interception, inertial impaction, gravitational settling, diffusion, and electrostatic attraction (Hinds 1999)....
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...This results in typical filtration efficiency curves with a minimum for particles of around 0.05 mm to 0.5 mm diameter (most penetrating particle size, Hinds 1999)....
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...…on number of material layers (Section 4.2) allows a more comprehensive comparison of the capabilities of potential filter materials using the filter quality factor qf (Hinds 1999; Huang et al. 2013): qf ¼ ln 1T Dp , (6) where T is the fractional transmission and Dp (in Pa) the pressure drop....
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...2) allows a more comprehensive comparison of the capabilities of potential filter materials using the filter quality factor qf (Hinds 1999; Huang et al. 2013):...
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Book•

Aerosol technology : properties, behavior, and measurement of airborne particles

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William C. Hinds

01 Jan 1999

TL;DR: Aerosol Technology, Second Edition as mentioned in this paper is the #1 guide to aerosol science and technology and has been the text of choice among students and professionals who need to acquire a thorough working knowledge of modern aerosol theory and applications.

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Abstract: The #1 guide to aerosol science and technology -now better than everSince 1982, Aerosol Technology has been the text of choice among students and professionals who need to acquire a thorough working knowledge of modern aerosol theory and applications. Now revised to reflect the considerable advances that have been made over the past seventeen years across a broad spectrum of aerosol-related application areas - from occupational hygiene and biomedical technology to microelectronics and pollution control -this new edition includes:* A chapter on bioaerosols* New sections on resuspension, transport losses, respiratory deposition models, and fractal characterization of particles* Expanded coverage of atmospheric aerosols, including background aerosols and urban aerosols* A section on the impact of aerosols on global warming and ozone depletion.Aerosol Technology, Second Edition also features dozens of new, fully worked examples drawn from a wide range of industrial and research settings, plus new chapter-end practice problems to help readers master the material quickly.

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3,237 citations