March 13, 2020
Disinfection of SARS-CoV-2 (COVID-19) in Human Respiratory Tract
by Controlled Ethanol Vapor Inhalation
Professor in Physics at OIST Graduate University
Okinawa Institute of Science and Technology Graduate University
1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, Japan 904-0495
Viruses such as SARS-CoV-2 and Influenza are lipophilic, enveloped viruses, and are relatively
easy to inactivate by exposure to alcohols. The envelope mainly consists of the lipid bilayer, taken
from the host cells at assembly/budding stage of the viral life cycle. Therefore the constitution of
the lipid bilayer should be common in all SARS, MERS and influenza viruses, even after mutations,
and thus these closely-related viruses will be disinfected by exposure to ethanol with the same
concentration. Existing experimental data indicate that an ethanol concentration of 30~40 v/v% is
sufficient to inactivate Influenza-A viruses in solution[1,2,3].
The author suggests that it may be possible to use alcoholic beverages of 16~20 v/v%
concentration for this disinfection process, such as Whisky (1:1 hot water dilution) or Japanese
Sake, because they are readily available and safe (non-toxic). By inhaling the alcohol vapor at
50~60°C (122~140°F) through the nose for one or two minutes, it will condense on surfaces inside
the respiratory tract; mainly in the nasal cavity. The alcohol concentration will be intensified to ~36
v/v% by this process, which is enough to disinfect the corona virus on the mucous membrane. In
this situation, our respiratory tract essentially works as an alcohol distillation apparatus (a
condenser). This method also provides more moisture into respiratory tract, and helps to clean the
inside of the nasal cavity by stimulating blowing of the nose, and also makes the mucous escalator
work actively so that the self-clearing mechanism in the trachea will remove viruses faster.
An alternative prompt method is also discussed. We use 40 v/v% whisky or similar alcohol,
dripping on a gauze, inhale the vapor slowly at room temperature. This method works well for the
front part of the nasal cavity. This is suitable for clinical workers, because they may need to use
prompt preventative measures at any time.
Alcohol for disinfection (rubbing alcohol in US, Surgical spirit B.P.) has been well established to
sterilize various bacterias and disinfect viruses. Alcohols target the bacterial cell envelope, with
resultant lysis of the cell and release of the cellular content. Also, it is well established that
lipophilic, enveloped viruses are easier to deactivate by alcohols than the non-enveloped viruses.
Nobuji Noda reported Influenza-A (USSR/92/97) was disinfected by a 1 minute exposure to
ethanol with a concentration of 30~40 v/v%. Recently Akemi Shinmyo reported careful
experimental results on five different strains of Influenza-A, where all viruses were disinfected by 1
minute exposure to ethanol at 27-36 v/v% (by reading result with reduction ratio 1/100). We
quickly performed the same test with a common laboratory E. coli strain (DH5alpha), and observed
that the bacterium becomes non-viable at an ethanol concentration of 30 v/v%. E. coli is a gram
negative bacteria, which also has a lipid outer layer and is thus sensitive to ethanol.
The novel coronavirus SARS-CoV-2 has recently emerged from China with a total of 113,702
laboratory-confirmed cases (as of March 9, 2020) . COVID-19 has become a global health
concern, and is causing huge economical impact due to freezing industrial activity closely linked
with supply chains in Wuhan, China, and blocking traffics in many countries. There is no vaccine
yet developed, and standard recommendations to prevent infection spread include regular hand
washing, and covering mouth and nose when coughing and sneezing. One of the problems is that
some spread might be possible before people show symptoms. Another problem is the suspected
longer incubation time associated with this virus. We urgently need an additional preventative
measure, which can stop, or at least slow down, the spread of this novel coronavirus.
In this paper, the author discuss possibility of disinfection of SARS-CoV-2 in our respiratory tract
via ethanol vapor inhalation.
2. Physics of Diffusion Phenomena
To use ethanol solution for disinfection, we have to understand the physics of diffusion and
evaporation. When we spray the ethanol solution on a surface for disinfection, for example, a door
knob, we have to be careful about the time-dependent decay of the ethanol concentration inside the
water droplet. As seen in the later section, the vapor pressure of ethanol is much higher than that of
water, thus ethanol evaporates faster, and the remaining solution becomes simple water quickly. The
mean-free path of molecules in solution is roughly 0.1 nm at room temperature, and it will take
more than times collisions for a molecule to travel a few micro-meters to reach the surface,
even in a straight pass, thus the diffusion phenomena dominates. The speed of evaporation of
ethanol can be estimated by the diffusion speed of ethanol molecules within a droplet. The simple
1D solution of the Fick’s diffusion law is
where D is the diffusion constant, which follows Einstein–Smoluchowski relation (kinetic theory)
where is the mobility, is the Boltzmann’s constant, T is the absolute temperature. For more
detail, we need to discuss the evaporation speed, which is equal to the probability of a molecule
escaping from the surface through enthalpy change in the Maxwell-Boltzmann distribution. This is
outside of the scope of this paper - we simply assume the diffusion dominates. The diffusion
constants of ethanol are listed in Table-1, and typical diffusion parameters are listed in Table-2.
Table-1 Diffusion constant of the ethanol molecule in water and air.
Table-2 Diffusion time and distance of the ethanol molecule in water and air.
An idea to use ethanol-water spray having 10 droplet size, for inhalation purposes, does not
work. The reason is that, as seen in Table-2, to travel 6 , it takes only 0.01 sec, and assuming 3
m/sec spray speed, the droplet after flying 30 mm in air, all ethanol will diffuse out. The droplets
become water, containing only low density ethanol, and thus will not be effective for disinfection.
Diffusion Constant (25 °C)
Ethanol in water solution
Ethanol vapor in air
Ethanol in Water Solution
Ethanol in Air
Thus, if we use the spray for ethanol disinfection experiments, the outcomes would fluctuate
greatly, and always higher concentration would be required. Also, in practice, the ethanol spray
should be avoided, because of possible fire accident.
Therefore, the author proposes inhalation of the ethanol vapor through the nose, which then
condenses inside our respiratory tract, and thus disinfects the corona virus.
3. How to Sterilize in our Respiratory Tract
As shown in Fig. 1, we inhale the ethanol vapor of alcohol solution at 50~60°C through the
nostrils using a tall cup (heat insulating styrofoam, or a wine glass). We fill ~30 ml Whisky, diluting
with 30 ml hot water (90°C). Half amount of them still works. The ethanol concentration becomes
~20%, and temperature goes 50~60°C. The cup should be brought close to the nose (press the rim
on to the lip), and the ethanol vapor should be inhaled. Mixing air and alcohol temperature change
do not affect on the ethanol concentration after condensation inside nasal cavity, but it is better to
keep air mixing as small as possible to minimize vapor condensation within the cup.
It will be better restrict our breathing to shallower breaths, in order to reduce alcohol condensation
in the trachea, where the important cilia-cells cover the surface and work for the mucous escalator
as the self-clearing mechanism of the airways. The mucous thickness in trachea is only 10 ,
and it takes only 0.01 sec for ethanol to reach the epithelium layer as shown in Table-2. In order to
minimize the risk of inflammation due to ethanol vapor (while the ethanol concentration is lowered
after traveling from nasal cavity to trachea), we have to limit the depth of breath.
Fig. 1 Inhaling the alcohol vapor through the nostrils for disinfection of viruses inside
the nasal cavity. Your respiratory tract as the alcohol distillation apparatus. This
illustration is reproduced from original image found in Wikipedia: https://
Figure 2 shows an example of controlled inhalation cycle. This is determined by the following
(1) Normally the breath volume of adult is 500 ml/ breath × 12 breaths/min .
(2) The so-called “dead space”, the volume of air that does not take part in the gas exchange, is
typically 150 ml. If the breath is smaller than dead space, ethanol does not go into the lung and is
not transferred into the blood.
(3) The volume of the nasal cavity of an adult is typically 30~37 ml . The breath volume must be
larger than this value. We assume 100 ml volume in each cycle.
(4) The surface area of the nasal cavity is roughly 100 cm2 , by taking account of nasal cavity
volume, average gap should be 6~8 mm. The diffusion time of an ethanol molecule for half of this
gap is roughly 0.3 sec in air estimated from Eq. (1). The inhalation cycle time has to be longer than
0.3 seconds, so that the ethanol molecules can reach the nasal surfaces. After this period, we have
to refresh the ethanol vapor, because most of ethanol molecules should be adsorbed into the mucous
membrane. The air flow inside the nasal cavity is turbulent, due to the narrow and complicated
pathway, which also accelerates the molecule adsorption speed. For more detail, we have to run
numerical simulations on air flow (fluid dynamics) and condensation (thermodynamics).
4. Ethanol Distillation Using Human Respiratory Tract
In this section, the pressures are written in (the standard atmosphere) unit. The
alcohol evaporates faster than the water. In physics term, this is expressed in terms of vapor
pressure. The vapor pressure of ethanol is higher than that of the water, that is why the alcohol
distillation process works. We utilize this principle to bring the ethanol into our respiratory tract at
higher concentration, efficiently and safely.
Before the detailed discussion, we have to note that the major gas component in the inhaling vapor
of alcohol is still normal air (nitrogen and oxygen). These species can also exist in liquid form, but
×105Pa ≈1a t m
Fig. 2. Example of the controlled inhalation cycle. The vertical axis is the volume change of lung
from the average volume at the relaxed breathing. During the inhalation, each breath should be
around 100 ml, and eight repeats of shallow inhalation/exhalation through nose should be performed,
followed by a few seconds of relaxed breathing outside the cup (providing oxygen). You may drink a
small amount of the alcohol, cleaning around the pharynx, if permitted according to your age and
local laws. We repeat this process for a few times, roughly one or two minutes in total. If you feel
drunken, you have to control the breath shallower.
their boiling temperatures are very low ( , ), and they will thus not
condense inside our body. Therefore we may neglect contributions from the air in the following
discussions. The presence of the air makes mass transfer speeds slower, but the ethanol
concentration in the condensed alcohol stays unchanged. We also neglect CO2 in the expired gas,
because it is a fairly small proportion. We treat only two components: ethanol and water in the
following discussions. Table 3 summarizes the major physical properties of ethanol and water.
The vapor pressure of pure material is given by the following Antoine equation, which is a semi-
empirical correlations describing the relation between vapor pressure and temperature for pure
where is the vapor pressure, T is temperature in °C and A, B and C are component-specific
constants. Those parameters are summarized in Table 4, and the vapor pressure curves for pure
ethanol and water are shown in Fig. 3. At 78.4 °C, the vapor pressure of the ethanol reaches to the
atmospheric pressure (1 atm), and thus boils.
Table 3. Physical property of ethanol and water.
Table 4. Parameter for Antoine equation: T in °C and pressure in Pa.
The total pressure is given by Dalton’s law,
where is the partial pressure of the component i in the gaseous mixture, which relies on the ideal
where V and T are the volume and absolute temperature in Kelvin (°K), R is the ideal gas constant.
is the amount of substance. In the current discussions, the temperature change is roughly 20 °K,
which is much smaller than room temperature (300 °K), thus we may assume temperature is
constant. Because all gas components share the same volume, we can normalize eq. (5) as ,
finally we have
log10 p* = A−B
Density (at 40 °C)
Heat of Vaporization (at 40 °C)
(Enthalpy of vaporization)
Tma x (∘C)
The partial pressure is equal to the normalized amount of substance.
The vapor pressure of mixture of liquids is given by Raoult's law. It states that the partial pressure
of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure
component multiplied by its mole fraction in the mixture .
where is the partial pressure of the component i in the gaseous mixture (above the solution),
is the equilibrium vapor pressure of the pure component given by eq. (3), is the mole fraction of
the component i in the mixture (in the solution). The ethanol and water mixture is not an ideal
solution, thus the actual vapor pressure shows negative or positive deviation due to the force acting
between molecules. However, as we see later, the actual mole fraction in our alcohol is only 0.07,
thus the deviation should be small, and we may treat our alcohol as an ideal solution.
Normally the concentration of alcohol is expressed using ABV: Alcohol By Volume, such as, 40 v/
v%. Raoult's law says the partial pressure is proportional to the mole fraction. We need to convert
ABV to mole-faction as follows.
where are the mole contents of ethanol and water in unit volume. Using densities of
and , we have
Using the definition of common ABV: Alcohol by volume (v/v%),
, . (10)
m1/46.1 + m2/18.0 =v1ρ1/46.1
v1ρ1/46.1 + v2ρ2/18.0
A BV =v1
v1/v2=A B V
Fig. 3. Vapor pressure curve of the pure ethanol and water.
Finally, the mole fraction of ethanol is given by
We use 20 v/v% alcohol (Whisky 1:1 water dilution), which is equal to mole fraction.
The water mole fraction is , which means most of the molecules in solution are
water. From Raoult's law, we find the partial pressures as follows. The mole contents are defined as
shown in Fig. 4.
At high temperature ;
After inhaling into our body, the gas will be cooled down.
At low temperature ;
The condensed mole contents are
Therefore, the mole fraction of ethanol in solution after condensation becomes
The concentration in ABV unit is
The condensed solution becomes ethanol solution of 36 v/v% concentration. This value is an ideal
case, i.e., the initial condition of the surface inside box is originally dry (the left box in Fig. 4).
There is water on the surface, i.e., the mucous membrane is 95 v/v% of water. The actual ethanol
concentration will have time dependent Gaussian distribution along its depth. For more detail, we
need to run numerical simulation.
x1=0.304 A BV
1−0.696 A BV
A BV =x1
0.304 + 0.696 x1
x2= 1 −x1= 0.93
1Hx1= 0.47 ×0.071 = 0.033
2Hx2= 0.20 ×0.93 = 0.19
1Lx1= 0.15 ×0.071 = 0.011
2Lx2= 0.061 ×0.93 = 0.057
m1=n1H−n1L= 0.033 −0.011 = 0.022
m2=n2H−n2L= 0.19 −0.057 = 0.13
A BV ′=y1
0.304 + 0.696 y1
Fig. 4. Mass transfer in the condensation process.
5. Prompt Method
We use 40 v/v% whisky or similar alcohol, dripping on a gauze, inhale the vapor slowly at room
(1) Drip 1~2 ml (1~2 g weight ) of alcohol 40 v/v%, such as, whisky, on a gauze.
(2) Cover your nostrils with gauze (point where you drip the alcohol).(3) Slowly and carefully
inhale the vapor. If one of your nostril has narrowing, block other one.
(4) After a few tens of seconds, the smell of the ethanol will disappear, then stop.
This method works well for the front part of the nasal cavity. This is suitable for clinical workers,
because their working environment means that they need may prompt preventative measure at short
notice. Note that there is a risk of inflammation due to high concentration of alcohol, but we have
to decide comparing with the risk from the corona virus itself. This method is only suggested for
use by medical professionals, and is not considered appropriate for use by the general public.
During the inhalation, the temperature of the alcohol drops to ~ 20°C due to heat of the
vaporization. Therefore the vapor pressure becomes much lower than the heating method, and
amount of the mass transfer (ethanol from gauze to nasal cavity) becomes roughly five times
smaller. The ethanol concentration will be determined by the mass balance between adsorption and
diffusion at the surface of mucous membrane. According to the rough estimate, it is around 30~40
v/v%. Further detail study is required.
The proposal discussed in this paper is still conceptual. We need further study on the following
(1) At this moment on March 2020, the author does not have reliable data on the ethanol
concentration required for disinfection of SARS-CoV-2. The author would like to ask
collaborators to perform experiment on this virus as soon as possible in any laboratory capable
of handling the virus safely.
(2) As discussed in Section. 2, the ethanol diffuses very quickly into water or coming out from
solution, and evaporates quickly. There is also heat exchange due to evaporation. Therefore, we
should be careful on how to evaluate actual ethanol concentration in the experiments.
(3) Generally speaking, the lipid becomes soft and active when it is warmed. Therefore, the above
mentioned experiments should be performed at the body temperature of 36.5°C, not at a room
temperature of 20°C.
(4) The side effects due to ethanol vapor inhalation are not yet evaluated, particularly, into the
trachea and the lung. Careful clinical trials under medical doctor supervision will be necessary.
(5) Alcohol inhalation is equivalent to “smoking ethanol vapor”. It will be required to discuss how
to control applications to persons below the age of legal consumption of alcohol, and also for
(6) Methanol(CH3OH) or methanol contained solution are highly prohibited to inhale, because of
(7) Once a day will be enough. It is better to perform this method at dinner time, and should not
drive car right after this.
The author discussed on possibility of disinfection of SARS-CoV-2 in human respiratory tract by
ethanol vapor inhalation. The alcohol distillation helps to raise the ethanol concentration on the
mucous membrane inside our recuperatory tract, where the viruses are suppose to remain and
incubate. Because of nature of the lipid bilayer (i.e. it is lipophilic), there is a chance to disinfect the
corona virus with alcohol vapor inhalation. The author would like to ask researchers in this field to
do more works on this method.
The author would like to thank Dr. Masao Yamashita and Dr. Ryusuke Kuwahara for their various
discussions and encouragements. The author also wishes to thank to Mr. Shuji Misumi and Mr.
Andrean Hanley for their help on checking equations, and thank to Mr. Seita Taba for laboratory
test of ethanol effect on E. coli. The author wishes to thank Dr. Cathal Cassidy for his careful
reading of the manuscript, and thank to Ms. Yoko Shintani for her various help.
 Seymour S. Block, “Disinfection, Sterilization and Preservation”, Fifth Edition, Lippincott
Williams & Wilkins, 2001, ISBN o-683-30740-1, p239.
 Nobuji NODA et. al., "Virucidal Activity of Alcohols, Virucidal Efficiency of Alcohols Against
Viruses in Liquid Phase", The Journal of the Japanese Association for Infection Diseases, Vol. 55,
 Akemi Shinmyo, “Effect of Density for Sterilization of Bacterias and Disinfection on Viruses”
doctoral thesis (in Japanese), Tokyo Health Care University, 2019.
 WHO, Novel Coronavirus (2019-nCoV). Situation Report 50, WHO (2020)
 A to Z of Thermodynamics by Pierre Perrot. ISBN 0-19-856556-9.
 Rama Bansil and Brandley S. Turner, “The biology of mucus: Composition, synthesis and
organization”, Advanced Drug Delivery Reviews 124 (2018) 3-15.
 Ganong's Review of Medical Physiology (24 ed.). ISBN 0071780033.
 Zheng J, Wang YP, Dong Z, Yang ZQ, Sun W., “Nasal cavity volume and nasopharyngeal cavity
volume in adults measured by acoustic rhinometry”, US National Library of Medicine National
Institutes of Health, 2000 No; 14 (11): 494-5
 Achim G. Beule, “Physiology and pathophysiology of respiratory mucosa of the nose and the
paranasal sinuses”, GMS Curr Top Otorhinolaryngol Head Neck Surg. 2010; 9: Doc07.
Supplemental Information (Appendix)
A1. Alcohols Beverages and Dilution Ratio
The following alcohols can be used. Unfortunately, most of the red and white wines do not have
high enough alcohol concentration. Liquors can be used by diluting with water. For example,
Whisky single shot amount (~30 ml) adding water 30 ml will be easy.
Table A1. Alternative alcohols and optimum dilution with water.
A2. The Cup
The plastic and paper cup for coffee will be good for minimizing heat loss, thus good for our
purpose. A red wine glass, with a broad bowl is the best.
Alcohol : Water
(Sherry, Port, Madeira & Others)
17 ~ 20%
as it is
higher than 16% is better
Plastic cups styrofoam made, paper cup with heat insulation, and
a red wine glass.
A3. How to measure the volume of alcohols.
The measuring cup for kitchen is the best to measure the volume. The shot glass is also useful.
Another good way is to measure the weight, where 100 ml = 100 g. The digital or mechanical
weight scale for kitchen is useful. Place an empty cup on the weight scale, pour alcohol for 30 mg,
then add 30 mg of hot water (1:1 dilution).
A4. How to heat.
(1) Whisky or others ~40 v/v%, refer the photos below.!
Boil water with a kettle. Pour the boiling water in an empty cup, or empty wine glass. Stop gas
or electric power of a boiling kettle. Wait one minute, then the temperature of boiled water in
the kettle become ~90°C (190°F). Empty the cup, pour a single shot or smaller amount of
Whisky. Pour the same amount of the hot water of 90°C (190°F) from the kettle, you have
55~60°C (122~140°F) of alcohol solution, ~20% of ethanol concentration. !
(2) Chinese Baijiu!
Same as Whisky. !
Or, dilute Baijiu with the same amount of water. Use a plastic and paper cup for coffee, heat in
a microwave oven. You need roughly 500 Watt x 30 sec for 100 ml (~100 g), see below.!
(3) Japanese sake or diluted Japanese Shochu.!
Use sake bottle, heat in hot water bath.!
Or heat with microwave oven. You need roughly 500 Watt x 30 sec for 100 ml (~100 g).
A5. Heating with microwave oven.
The microwave oven is a good way to heat. But, you need practice. The microwave power and
required heating times are summarized in Table A4. You should try to heat with the tap water first,
and measure the temperature with a thermometer. If temperature is higher than 60°C (140°F),
reduce heating time.
Required time can be estimated by , where t is time in seconds, W is weight of
the alcohol solution, dT is heating temperature from the room temperature in °C, P is power of the
microwave oven in Watt. The cup itself need to be heated, so that you need prior test.
Total volume (weight)
Heating Power and Time
from room temperature at 15°C (60°F)
to 60 °C (140°F).
Heating Power and Time
from temperature at 25°C (77°F)
to 60 °C (140°F).
60 ml (60 g)
500 W x 23 sec, 600 W x 19 sec
500 W x 18 sec, 600 W x 15 sec
100 ml (100 g)
500 W x 38 sec, 600 W x 33 sec
500 W x 30 sec, 600 W x 25 sec
— End of supplemental information —
How to make the alcohol solution.