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Visualizing the effectiveness of face masks in obstructing respiratory jets
Siddhartha Verma,1,a) Manhar Dhanak,1, b) and John Frankenfield1, c)
Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton,
FL 33431, USA
(Dated: 4 June 2020)
The use of face masks in public settings has been widely recommended by public health officials during the current
COVID-19 pandemic. The masks help mitigate the risk of cross-infection via respiratory droplets, however, there are no
specific guidelines on mask materials and designs that are most effective in minimizing droplet dispersal. While there
have been prior studies on the performance of medical-grade masks, there is insufficient data on cloth-based coverings
which are being used by a vast majority of the general public. We use qualitative visualizations of emulated coughs
and sneezes to examine how material- and design-choices impact the extent to which droplet-laden respiratory jets are
blocked. Loosely folded face masks and bandana-style coverings provide minimal stopping-capability for the smallest
aerosolized respiratory droplets. Well-fitted homemade masks with multiple layers of quilting fabric, and off-the-shelf
cone style masks, proved to be the most effective in reducing droplet dispersal. These masks were able to curtail the
speed and range of the respiratory jets significantly, albeit with some leakage through the mask material and from small
gaps along the edges. Importantly, uncovered emulated coughs were able to travel noticeably farther than the currently
recommended 6-foot distancing guideline. We outline the procedure for setting up simple visualization experiments
using easily available materials, which may help healthcare professionals, medical researchers, and manufacturers in
assessing the effectiveness of face masks and other personal protective equipment qualitatively.
Infectious respiratory illnesses can exact a heavy socio-
economic toll on the most vulnerable members of our soci-
ety, as has become evident from the current COVID-19 pan-
demic1,2. The disease has overwhelmed healthcare infrastruc-
ture worldwide3, and its high contagion rate and relatively
long incubation period4,5 have made it difficult to trace and
isolate infected individuals. Current estimates indicate that
about 35% of infected individuals do not display overt symp-
toms6, and may contribute to significant spread of the dis-
ease without their knowledge. In an effort to contain the un-
abated community spread of the disease, public health offi-
cials have recommended the implementation of various pre-
ventative measures, including social-distancing and the use of
face masks in public settings7.
The rationale behind the recommendation for using masks
or other face coverings is to reduce the risk of cross-infection
via the transmission of respiratory droplets from infected to
healthy individuals8,9. The pathogen responsible for COVID-
19 is found primarily in respiratory droplets that are expelled
by infected individuals during coughing, sneezing, or even
talking and breathing10–15. Apart from COVID-19, respira-
tory droplets are also the primary means of transmission for
various other viral and bacterial illnesses, such as the common
cold, influenza, tuberculosis, SARS (Severe Acute Respira-
tory Syndrome), and MERS (Middle East Respiratory Syn-
drome), to name a few16–19. These pathogens are enveloped
within respiratory droplets, which may land on healthy in-
dividuals and result in direct transmission, or on inanimate
objects which can lead to infection when a healthy individ-
ual comes in contact with them10,18,20,21. In another mode of
a)Electronic mail: vermas@fau.edu; http://www.computation.fau.edu; Also
at Harbor Branch Oceanographic Institute, Florida Atlantic University, Fort
Pierce, FL 34946, USA
b)Electronic mail: dhanak@fau.edu
c)Electronic mail: jfranken@fau.edu
transmission, the droplets or their evaporated contents may re-
main suspended in the air for long periods of time if they are
sufficiently small. This can lead to airborne transmission19,22
when they are breathed in by another person, long after the
infected individual may have left the area.
Several studies have investigated respiratory droplets pro-
duced by both healthy and infected individuals when per-
forming various activities. The transport characteristics of
these droplets can vary significantly depending on their diam-
eter23–28. The reported droplet diameters vary widely among
studies available in the literature, and usually lie within the
range 1µm500µm29 , with a mean diameter of approxi-
mately 10µm30. The larger droplets (diameter > 100µm)
are observed to follow ballistic trajectories under the ef-
fects of gravity and aerodynamic drag20,31. Intermediate-
sized droplets20,31,32 may get carried over considerable dis-
tances within a multiphase turbulent cloud33–35. The smallest
droplets and particles (diameter < 5µmto 10µm) may remain
suspended in the air indefinitely, until they are carried away
by a light breeze or ventilation airflow20,32.
After being expelled into the ambient environment, the res-
piratory droplets experience varying degrees of evaporation
depending on their size, the ambient humidity, and tempera-
ture. The smallest droplets may undergo complete evapora-
tion, leaving behind a dried-out spherical mass consisting of
the particulate contents (e.g., pathogens), which are referred to
as ‘droplet nuclei’36. These desiccated nuclei, in combination
with the smallest droplets, are potent transmission sources on
account of two factors: 1) they can remain suspended in the air
for hours after the infected individual has left the area, poten-
tially infecting unsuspecting individuals who come into con-
tact with them; and 2) they can penetrate deep into the airways
of individuals who breathe them in, which increases the likeli-
hood of infection even for low pathogen loads. At present, the
role of droplet nuclei in the transmission of COVID-19 is not
known with certainty, and the matter is the subject of ongoing
studies37–39. In addition to generating microscopic droplets,
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the action of sneezing can expel sheet-like layers of respi-
ratory fluids40, which may break apart into smaller droplets
through a series of instabilities. The majority of the fluid con-
tained within the sheet falls to the ground quickly within a
short distance.
Regardless of their size, all droplets and nuclei expelled by
infected individuals are potential carriers of pathogens. Var-
ious studies have investigated the effectiveness of medical-
grade face masks and other personal protective equipment
(PPE) in reducing the possibility of cross-infection via these
droplets13,33,41–47. Notably, such respiratory barriers do
not prove to be completely effective against extremely fine
aerosolized particles, droplets, and nuclei. The main is-
sue tends to be air leakage, which can result in aerosolized
pathogens being dispersed and suspended in the ambient en-
vironment for long periods of time after a coughing/sneezing
event has occurred. A few studies have considered the filtra-
tion efficiency of homemade masks made with different types
of fabric48–51, however there is no broad consensus regarding
their effectiveness in minimizing disease transmission52,53.
Nonetheless, the evidence suggests that masks and other face
coverings are effective in stopping larger droplets, which al-
though fewer in number compared to the smaller droplets and
nuclei, constitute a large fraction of the total volume of the
ejected respiratory fluid.
While detailed quantitative measurements are necessary for
comprehensive characterization of PPE, qualitative visualiza-
tions can be invaluable for rapid iteration in early design
stages, as well as for demonstrating the proper use of such
equipment. Thus, one of the aims of this letter is to describe a
simple setup for visualization experiments, which can be as-
sembled using easily available materials. Such setups may be
helpful to healthcare professionals, medical researchers, and
to industrial manufacturers, for assessing the effectiveness of
face masks and other protective equipment qualitatively. Test-
ing designs quickly and early on can prove to be crucial, es-
pecially in the current pandemic scenario where one of the
central objectives is to reduce the severity of the anticipated
resurgence of infections in the upcoming months.
The visualization setup used in the current study is shown
in Figure 1, and consists of a hollow manikin head which was
padded on the inside to approximate the internal shape and
volume of the nasal- and buccal-cavities in an adult. In case
a more realistic representation is required, such a setup could
include 3D-printed or silicone models of the internal airways.
The manikin was mounted at a height of approximately 5 feet
and 8 inches to emulate respiratory jets expelled by an average
human male. The circular opening representing the mouth is
0.75 inches in diameter. The pressure impulse that emulates
a cough or a sneeze may be delivered via a manual pump as
shown in Figure 1, or via other sources such as an air com-
pressor or a pressurized air canister. The air capacity of the
pump is 500ml, which is comparable to the lower end of the
total volume expelled during a cough54. We note that the setup
here emulates a simplified representation of an actual cough,
which is an extremely complex and dynamic problem55.We
use a recreational fog/smoke machine to generate tracer par-
ticles for visualizing the expelled respiratory jets, using a liq-
Smoke
Generator
Manual
Pump
Face Mask
FIG. 1: Left - Experimental setup for qualitative
visualization of emulated coughs and sneezes. Right - A laser
sheet illuminates a puff emerging from the mouth.
uid mixture of distilled water (4 parts) and glycerin (1 part).
Both the pressure- and smoke-sources were connected to the
manikin using clear vinyl tubing and NPT fittings wherever
necessary.
The resulting ‘fog’ or ‘smoke’ is visible in the right panel
of Figure 1, and is composed of microscopic droplets of the
vaporized liquid mixture. These are comparable in size to
the smallest droplets expelled in a cough jet (approximately
1µmto 10µm). We estimate that the fog droplets are less than
10µmin diameter, based on Stokes’ law and our observation
that they could remain suspended for up to 3 minutes in com-
pletely still air with no perceptible settling. The laser source
used to generate the visualization sheet is an off-the-shelf
5mW green laser pointer with a 532nm wavelength. A plane
vertical sheet is created by passing the laser beam through
a thin cylindrical rod (diameter 5mm) made of borosilicate
glass.
We first present visualization results from an emulation of
an uncovered heavy cough. The spatial and temporal evolu-
tion of the resulting jet is shown in Figure 2. The aerosolized
microscopic droplets visible in the laser sheet act as tracer
particles, revealing a 2-dimensional cross section of the con-
ical turbulent jet. These tracers depict the fate of the small-
est ejected droplets, and any resulting nuclei that may form.
We observed high variability in droplet dispersal patterns from
one experimental run to another, which was caused by other-
wise imperceptible changes in the ambient airflow. This high-
lights the importance of designing ventilation systems that
specifically aim to minimize the possibility of cross-infection
in a confined setting23,56–58.
Despite high variability, we consistently observed jets that
travelled farther than the 6-foot minimum distance proposed
by the U.S. Centers for Disease Control and Prevention7. In
the images shown in Figure 2, the ejected tracers were ob-
served to travel up to 12 feet within approximately 50 seconds.
Moreover, the tracer droplets remained suspended midair for
up to 3 minutes in the quiescent environment. These obser-
vations, in combination with other recent studies35,59, suggest
that current social-distancing guidelines may need to be up-
dated to account for aerosol-based transmission of pathogens.
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3 feet
(a)
6 feet
3 feet
(b)
6 feet
9 feet
12 feet
3 feet
(c)
FIG. 2: An emulated heavy cough jet travels up to 12 feet in approximately 50 seconds, which is twice the CDC’s recommended
distancing guideline of 6 feet7. (a) 2.3 seconds after initiation of the emulated cough (b) 11 seconds (c) 53 seconds.
We note that although the unobstructed turbulent jets were ob-
served to travel up to 12 feet, a large majority of the ejected
droplets will fall to the ground by this point. Importantly, both
the number and concentration of the droplets will decrease
with increasing distance59, which is the fundamental rationale
behind social-distancing.
We now discuss dispersal patterns observed when the
mouth opening was blocked using three different types of face
masks. For these results, we focus on masks that are read-
ily accessible to the general public, and which do not draw
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away from the supply of medical-grade masks and respirators
for healthcare workers. Figure 3 shows the impact of using a
folded cotton handkerchief mask on the expelled respiratory
jet. The folded mask was constructed by following instruc-
tions recommended by the U.S. Surgeon General60. It is evi-
dent that while the forward motion of the jet is impeded sig-
nificantly, there is notable leakage of tracer droplets through
the mask material. We also observe a small amount of trac-
ers escaping from the top edge of the mask, where gaps ex-
ist between the nose and the cloth material. These droplets
remained suspended in the air until they were dispersed by
ambient disturbances. In addition to the folded handkerchief
mask discussed here, we tested a single-layer bandana-style
covering (not shown) which proved to be substantially less ef-
fective in stopping the jet and the tracer droplets.
We now examine a homemade mask that was stitched using
two-layers of cotton quilting fabric consisting of 70 threads
per inch. The mask’s impact on droplet dispersal is shown in
Figure 4. We observe that the mask is able to arrest the for-
ward motion of the tracer droplets almost completely. There
is minimal forward leakage through the material, and most of
the tracer-escape happens from the gap between the nose and
the mask along the top edge. The forward distance covered by
the leaked jet is less than 3 inches in this case. The final mask
design that we tested was a non sterile cone-style mask that
is available in most pharmacies. The corresponding droplet-
dispersal visualizations are shown in Figure 5, which indicate
that the flow is impeded significantly compared to Figure 2
and Figure 3. However, there is noticeable leakage from gaps
along the top edge. The forward distance coverd by the leaked
jet is approximately 6 inches from the mouth opening, which
is farther than the distance for the stitched mask in Figure 4.
A summary of the various scenarios examined in this study
is provided in Table I, along with details about the mask ma-
terial and the average distances travelled by the respiratory
jets. We observe that a single-layer bandana-style covering
can reduce the range of the expelled jet to some extent, com-
pared to an uncovered cough. Importantly, both the mate-
rial and construction technique have a notable impact on the
masks’ stopping-capability. The stitched mask made of quilt-
ing cotton was observed to be the most effective, followed by
the commercial mask, the folded handkerchief, and finally,
the bandana. Importantly, our observations suggest that a
higher thread count by itself is not sufficient to guarantee bet-
ter stopping-capability; the bandana covering, which has the
highest thread count among all the cloth masks tested, turned
out to be the least effective.
We note that it is likely that healthcare professionals trained
properly in the use of high-quality fitted masks will not ex-
perience leakage to the extent that we have observed in this
study. However, leakage remains a likely issue for members
of the general public who often rely on loose-fitting home-
made masks. Additionally, the masks may get saturated after
prolonged use, which might also influence their filtration ca-
pability. We reiterate that although the non-medical masks
tested in this study experienced varying degrees of flow leak-
age, they are likely to be effective in stopping larger respira-
tory droplets.
In addition to providing an initial indication of the effec-
tiveness of protective equipment, the visuals used in this study
can help convey to the general public the rationale behind
social-distancing guidelines and recommendations for using
face masks. Promoting widespread awareness of effective pre-
ventative measures is crucial, given the high likelihood of a
resurgence of COVID-19 infections in the fall and winter.
DATA AVAIL ABIL ITY
The data that supports the findings of this study is available
within the article.
1United Nations, “A UN framework for the immediate socio-economic re-
sponse to COVID-19,” Tech. Rep. April (United Nations, 2020).
2M. Nicola, Z. Alsafi, C. Sohrabi, A. Kerwan, A. Al-Jabir, C. Iosifidis,
M. Agha, and R. Agha, “The socio-economic implications of the coron-
avirus pandemic (COVID-19): A review,” International journal of surgery
(London, England) 78, 185–193 (2020).
3E. J. Emanuel, G. Persad, R. Upshur, B. Thome, M. Parker, A. Glick-
man, C. Zhang, C. Boyle, M. Smith, and J. P. Phillips, “Fair Allocation
of Scarce Medical Resources in the Time of Covid-19,” New England Jour-
nal of Medicine 382, 2049–2055 (2020).
4S. A. Lauer, K. H. Grantz, Q. Bi, F. K. Jones, Q. Zheng, H. R. Mered-
ith, A. S. Azman, N. G. Reich, and J. Lessler, “The Incubation Period
of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Con-
firmed Cases: Estimation and Application,” Annals of Internal Medicine
172, 577–582 (2020).
5X. He, E. H. Y. Lau, P. Wu, X. Deng, J. Wang, X. Hao, Y. C. Lau,
J. Y. Wong, Y. Guan, X. Tan, X. Mo, Y. Chen, B. Liao, W. Chen, F. Hu,
Q. Zhang, M. Zhong, Y. Wu, L. Zhao, F. Zhang, B. J. Cowling, F. Li, and
G. M. Leung, “Temporal dynamics in viral shedding and transmissibility of
COVID-19,” Nature Medicine 26, 672–675 (2020).
6Centers for Disease Control and Prevention, “COVID-19 Pan-
demic Planning Scenarios,” https://www.cdc.gov/coronavirus/2019-
ncov/hcp/planning-scenarios.html (May, 2020).
7Centers for Disease Control and Prevention, “Social Distancing, Quaran-
tine, and Isolation,” https://www.cdc.gov/coronavirus/2019-ncov/prevent-
getting-sick/social-distancing.html (May, 2020).
8C. R. MacIntyre, S. Cauchemez, D. E. Dwyer, H. Seale, P. Cheung,
G. Browne, M. Fasher, J. Wood, Z. Gao, R. Booy, and N. Ferguson,
“Face mask use and control of respiratory virus transmission in house-
holds,” Emerging infectious diseases 15, 233–241 (2009).
9C. R. MacIntyre and A. A. Chughtai, “A rapid systematic review of the
efficacy of face masks and respirators against coronaviruses and other res-
piratory transmissible viruses for the community, healthcare workers and
sick patients,” International Journal of Nursing Studies , 103629 (2020).
10L. Morawska, “Droplet fate in indoor environments, or can we prevent the
spread of infection?” Indoor Air 16, 335–347 (2006).
11S. Stelzer-Braid, B. G. Oliver, A. J. Blazey, E. Argent, T. P. Newsome,
W. D. Rawlinson, and E. R. Tovey, “Exhalation of respiratory viruses by
breathing, coughing, and talking,” Journal of Medical Virology 81, 1674–
1679 (2009).
12L. Morawska, G. R. Johnson, Z. D. Ristovski, M. Hargreaves,
K. Mengersen, S. Corbett, C. Y. H. Chao, Y. Li, and D. Katoshevski, “Size
distribution and sites of origin of droplets expelled from the human res-
piratory tract during expiratory activities,” Journal of Aerosol Science 40,
256–269 (2009).
13C. Chen, C. H. Lin, Z. Jiang, and Q. Chen, “Simplified models for exhaled
airflow from a cough with the mouth covered,” Indoor Air 24, 580–591
(2014).
14V. Stadnytskyi, C. E. Bax, A. Bax, and P. Anfinrud, “The airborne life-
time of small speech droplets and their potential importance in SARS-CoV-
2 transmission,” Proceedings of the National Academy of Sciences , 3–5
(2020).
15P. Bahl, C. Doolan, C. de Silva, A. A. Chughtai, L. Bourouiba, and C. R.
MacIntyre, “Airborne or Droplet Precautions for Health Workers Treat-
This is the author’s peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.
PLEASE CITE THIS ARTICLE AS DOI:10.1063/5.0016018
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2 in
(a)
Leakage from
the top
Leakage through
the mask
(b)
(c) (d)
FIG. 3: (a) A face mask constructed using a folded handkerchief. (b) 0.5 seconds after initiation of the emulated cough (c) 2.27
seconds (d) 5.55 seconds.
2 in
(a)
Leakage from
the top
(b)
Leakage through
the mask
(c) (d)
FIG. 4: (a) A homemade face mask stitched using two-layers of cotton quilting fabric. (b) 0.2 seconds after initiation of the
emulated cough (c) 0.47 seconds (d) 1.68 seconds.
ing Coronavirus Disease 2019?” The Journal of Infectious Diseases , 1–8
(2020).
16L. C. Jennings and E. C. Dick, “Transmission and control of rhinovirus
colds,” European Journal of Epidemiology 3, 327–335 (1987).
17Centers for Disease Control and Prevention, “Core Curriculum on Tuber-
culosis : What the Clinician Should Know,” Tech. Rep. (2013).
18J. S. Kutter, M. I. Spronken, P. L. Fraaij, R. A. Fouchier, and S. Herfst,
“Transmission routes of respiratory viruses among humans,” Current Opin-
ion in Virology 28, 142 – 151 (2018).
19R. Tellier, Y. Li, B. J. Cowling, and J. W. Tang, “Recognition of aerosol
transmission of infectious agents: A commentary,” BMC Infectious Dis-
eases 19, 1–9 (2019).
This is the author’s peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.
PLEASE CITE THIS ARTICLE AS DOI:10.1063/5.0016018
6
2 in
(a)
Leakage from
the top
(b)
Leakage through
the mask
Leading
plume
(c) (d)
FIG. 5: (a) An off-the-shelf cone style mask. (b) 0.2 seconds after initiation of the emulated cough (c) 0.97 seconds. The
leading plume, which has dissipated considerably, is faintly visible. (d) 3.7 seconds.
TABLE I: A summary of the different types of masks tested, the materials they are made of, and their effectiveness in impeding
droplet-dispersal. The last column indicates the distance travelled by the jet beyond which its forward progression stops. The
average distances have been computed over multiple runs, and the symbol ‘⇠’ is used to indicate the presence of high
variability in the first two scenarios listed.
Mask type Material Threads per inch Average jet distance
Uncovered — — ⇠8 feet
Bandana Elastic T-shirt material 85 ⇠3 feet 7 inches
Folded handkerchief Cotton 55 1 foot 3 inches
Stitched mask Quilting cotton 70 2.5 inches
Commercial maskaUnknown Randomly assorted fibers 8 inches
aCVS Cone Face Mask
20R. Tellier, “Review of aerosol transmission of influenza A virus,” Emerging
infectious diseases 12, 1657–1662 (2006).
21A. Fernstrom and M. Goldblatt, “Aerobiology and Its Role in the Transmis-
sion of Infectious Diseases,” Journal of Pathogens 2013, 1–13 (2013).
22J. W. Tang, C. J. Noakes, P. V. Nielsen, I. Eames, A. Nicolle, Y. Li, and
G. S. Settles, “Observing and quantifying airflows in the infection control
of aerosol- and airborne-transmitted diseases: An overview of approaches,”
Journal of Hospital Infection 77, 213–222 (2011).
23J. W. Tang, Y. Li, I. Eames, P. K. S. Chan, and G. L. Ridgway, “Factors
involved in the aerosol transmission of infection and control of ventilation
in healthcare premises,” Journal of Hospital Infection 64, 100–114 (2006).
24S. W. Zhu, S. Kato, and J. H. Yang, “Study on transport characteristics
of saliva droplets produced by coughing in a calm indoor environment,”
Building and Environment 41, 1691–1702 (2006).
25X. Xie, Y. Li, A. T. Y. Chwang, P. L. Ho, and W. H. Seto, “How far droplets
can move in indoor environments – revisiting the Wells evaporation–falling
curve,” Indoor Air 17, 211–225 (2007).
26S. Liu and A. Novoselac, “Transport of airborne particles from an un-
obstructed cough jet,” Aerosol Science and Technology 48, 1183–1194
(2014).
27H. Nishimura, S. Sakata, and A. Kaga, “A new methodology for studying
dynamics of aerosol particles in sneeze and cough using a digital high-
vision, high-speed video system and vector analyses,” PLoS ONE 8(2013).
28J. Gralton, E. Tovey, M. L. McLaws, and W. D. Rawlinson, “The role of
particle size in aerosolised pathogen transmission: A review,” Journal of
Infection 62, 1–13 (2011).
29Z. Y. Han, W. G. Weng, and Q. Y. Huang, “Characterizations of particle
size distribution of the droplets exhaled by sneeze,” Journal of the Royal
Society Interface 10 (2013).
30C. Y. Chao, M. P. Wan, L. Morawska, G. R. Johnson, Z. D. Ristovski,
M. Hargreaves, K. Mengersen, S. Corbett, Y. Li, X. Xie, and D. Kato-
shevski, “Characterization of expiration air jets and droplet size distribu-
tions immediately at the mouth opening,” Journal of Aerosol Science 40,
122–133 (2009).
31W. F. Wells, “On air-borne infection: Study II. Droplets and droplet nuclei.”
American Journal of Epidemiology 20, 611–618 (1934).
32J. P. Duguid, “The size and the duration of air-carriage of respiratory
droplets and droplet-nuclei,” The Journal of hygiene 78, 471–479 (2020).
33J. W. Tang, T. J. Liebner, B. A. Craven, and G. S. Settles, “A schlieren
optical study of the human cough with and without wearing masks for
aerosol infection control,” Journal of the Royal Society Interface 6, 727–
736 (2009).
34L. Bourouiba, E. Dehandschoewercker, and J. W. Bush, “Violent expiratory
events: On coughing and sneezing,” Journal of Fluid Mechanics 745, 537–
563 (2014).
35L. Bourouiba, “Turbulent Gas Clouds and Respiratory Pathogen Emissions:
Potential Implications for Reducing Transmission of COVID-19,” JAMA -
Journal of the American Medical Association , E1–E2 (2020).
36M. Nicas, W. W. Nazaroff, and A. Hubbard, “Toward Understanding the
Risk of Secondary Airborne Infection: Emission of Respirable Pathogens,”
Journal of Occupational and Environmental Hygiene 2, 143–154 (2005).
37Y. Liu, Z. Ning, Y. Chen, M. Guo, Y. Liu, N. K. Gali, L. Sun, Y. Duan,
J. Cai, D. Westerdahl, X. Liu, K. Xu, K.-f. Ho, H. Kan, Q. Fu, and K. Lan,
“Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals,” Nature
(2020).
38S. W. X. Ong, Y. K. Tan, P. Y. Chia, T. H. Lee, O. T. Ng, M. S. Y. Wong,
and K. Marimuthu, “Air, Surface Environmental, and Personal Protective
Equipment Contamination by Severe Acute Respiratory Syndrome Coron-
avirus 2 (SARS-CoV-2) From a Symptomatic Patient,” JAMA - Journal of
This is the author’s peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.
PLEASE CITE THIS ARTICLE AS DOI:10.1063/5.0016018
7
the American Medical Association 323, 1610–1612 (2020).
39J. Cai, W. Sun, J. Huang, M. Gamber, J. Wu, and G. He, “Indirect Virus
Transmission in Cluster of COVID-19 Cases, Wenzhou, China, 2020,”
Emerging infectious diseases 26, 1343–1345 (2020).
40B. E. Scharfman, A. H. Techet, J. W. Bush, and L. Bourouiba, “Visual-
ization of sneeze ejecta: steps of fluid fragmentation leading to respiratory
droplets,” Experiments in Fluids 57, 1–9 (2016).
41G. B. Ha’eri and A. M. Wiley, “The Efficacy of Standard Surgical Face
Masks: An Investigation Using ‘Tracer Particles’,” Clinical Orthopaedics
and Related Research 148 (1980).
42D. F. Johnson, J. D. Druce, C. Birch, and M. L. Grayson, “A Quantitative
Assessment of the Efficacy of Surgical and N95 Masks to Filter Influenza
Virus in Patients with Acute Influenza Infection,” Clinical Infectious Dis-
eases 49, 275–277 (2009).
43W. G. Lindsley, W. P. King, R. E. Thewlis, J. S. Reynolds, K. Panday,
G. Cao, and J. V. Szalajda, “Dispersion and exposure to a cough-generated
aerosol in a simulated medical examination room,” Journal of Occupational
and Environmental Hygiene 9, 681–690 (2012).
44W. G. Lindsley, J. D. Noti, F. M. Blachere, J. V. Szalajda, and D. H.
Beezhold, “Efficacy of face shields against cough aerosol droplets from a
cough simulator,” Journal of Occupational and Environmental Hygiene 11,
509–518 (2014).
45G. Zayas, M. C. Chiang, E. Wong, F. Macdonald, C. F. Lange, A. Senthil-
selvan, and M. King, “Effectiveness of cough etiquette maneuvers in dis-
rupting the chain of transmission of infectious respiratory diseases,” BMC
Public Health 13, 1–11 (2013).
46N. H. L. Leung, D. K. W. Chu, E. Y. C. Shiu, K.-H. Chan, J. J. McDevitt,
B. J. P. Hau, H.-L. Yen, Y. Li, D. K. M. Ip, J. S. M. Peiris, W.-H. Seto, G. M.
Leung, D. K. Milton, and B. J. Cowling, “Respiratory virus shedding in
exhaled breath and efficacy of face masks,” Nature Medicine 26, 676–680
(2020).
47S. S. Zhou, S. Lukula, C. Chiossone, R. W. Nims, D. B. Suchmann, and
M. K. Ijaz, “Assessment of a respiratory face mask for capturing air pollu-
tants and pathogens including human influenza and rhinoviruses,” Journal
of thoracic disease 10, 2059–2069 (2018).
48S. Rengasamy, B. Eimer, and R. E. Shaffer, “Simple Respiratory Protec-
tion—Evaluation of the Filtration Performance of Cloth Masks and Com-
mon Fabric Materials Against 20–1000 nm Size Particles,” The Annals of
Occupational Hygiene 54, 789–798 (2010).
49A. Davies, K.-A. Thompson, K. Giri, G. Kafatos, J. Walker, and A. Ben-
nett, “Testing the efficacy of homemade masks: Would they protect in an
influenza pandemic?” Disaster Medicine and Public Health Preparedness 7,
413–418 (2013).
50S. Bae, M.-C. Kim, J. Y. Kim, H.-H. Cha, J. S. Lim, J. Jung, M.-J. Kim,
D. K. Oh, M.-K. Lee, S.-H. Choi, M. Sung, S.-B. Hong, J.-W. Chung,
and S.-H. Kim, “Effectiveness of Surgical and Cotton Masks in Blocking
SARS-CoV-2: A Controlled Comparison in 4 Patients,” Annals of internal
medicine , M20–1342 (2020).
51A. Konda, A. Prakash, G. A. Moss, M. Schmoldt, G. D. Grant, and S. Guha,
“Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory
Cloth Masks,” ACS Nano 14, 6339–6347 (2020).
52S. Feng, C. Shen, N. Xia, W. Song, M. Fan, and B. J. Cowling, “Rational
use of face masks in the COVID-19 pandemic,” The Lancet Respiratory
Medicine 8, 434–436 (2020).
53J. Xiao, E. Y. C. Shiu, H. Gao, J. Y. Wong, M. W. Fong, S. Ryu, and
B. J. Cowling, “Nonpharmaceutical measures for pandemic influenza in
nonhealthcare settings-personal protective and environmental measures,”
Emerging infectious diseases 26, 967–975 (2020).
54J. K. Gupta, C.-H. Lin, and Q. Chen, “Flow dynamics and characterization
of a cough,” Indoor Air 19, 517–525 (2009).
55J. Hsu, R. Stone, R. Logan-Sinclair, M. Worsdell, C. Busst, and K. Chung,
“Coughing frequency in patients with persistent cough: assessment using a
24 hour ambulatory recorder,” European Respiratory Journal 7, 1246–1253
(1994).
56E. Bjørn and P. V. Nielsen, “Dispersal of exhaled air and personal exposure
in displacement ventilated rooms,” Indoor Air 12, 147–164 (2002).
57H. Qian, Y. Li, P. V. Nielsen, C. E. Hyldgaard, T. W. Wong, and A. T. Y.
Chwang, “Dispersion of exhaled droplet nuclei in a two-bed hospital ward
with three different ventilation systems,” Indoor Air 16, 111–128 (2006).
58Y. Li, G. M. Leung, J. W. Tang, X. Yang, C. Y. Chao, J. Z. Lin, J. W. Lu,
P. V. Nielsen, J. Niu, H. Qian, A. C. Sleigh, H. J. Su, J. Sundell, T. W. Wong,
and P. L. Yuen, “Role of ventilation in airborne transmission of infectious
agents in the built environment - A multidisciplinary systematic review,”
Indoor Air 17, 2–18 (2007).
59T. Dbouk and D. Drikakis, “On coughing and airborne droplet transmission
to humans,” Physics of Fluids 32, 053310 (2020).
60Centers for Disease Control and Prevention (CDC), “How to Make Your
own Face Covering,” https://www.youtube.com/watch?v=tPx1yqvJgf4
(2020).
This is the author’s peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.
PLEASE CITE THIS ARTICLE AS DOI:10.1063/5.0016018
