Increased indoor humidity may decrease #Coronavirus #COVID-19 transmission

Note: The suggestions in this guest essay may or may not be useful in your personal situation. It is provided here for review and discussion. There is some supporting evidence that increased heat and humidity will have an adverse affect on the Coronovirus, as does UV-C light, but each personal situation is unique, and other factors may dominate transmission likelihoods. Use your own best judgment. – Anthony


Guest essay by Leo Goldstein

Bullet points:

  • COVID-19 spreads mostly indoors by person to person and person to surface to person transmission
  • Increasing humidity indoors to 50%-60% is a safe and promising method to fight COVID-19 spread

Increasing Indoor Humidity to Constrain COVID-19

Indoor temperature, humidity, and ventilation must be increased in public and private buildings in all COVID-19 affected areas. Here, indoor temperature of at least 75°F (24°C) and relative humidity levels of 50%-60% are recommended.

Summary

It is a common knowledge, confirmed by the rigorous body of research, that low temperatures and low humidity contribute to flu-like virus epidemics, while high temperatures and high humidity reduce or even prevent flu-like epidemics. Good ventilation (rapid exchange of indoor air, which potentially contains viruses, with clean outside air) is another important factor that decreases the virus spread. COVID-19 is caused by a coronavirus SARS-CoV-2. Coronaviruses and Influenza viruses are enveloped RNA viruses from the respiratory virus group.  Therefore, the knowledge gained by the vast amount of prior studies of such viruses is fully applicable to the current epidemic.

People in the US and other developed countries spend most of their time indoors. The typical indoor conditions are characterized by very low relative humidity, lower than optimal temperature, and bad ventilation. Today, the seasonality of flu-like illnesses is better explained as an indirect impact of cold weather. Heating without humidification dries indoor air, and the low humidity contributes to virus survival, infectivity preservation, and transmission. There is evidence that these indoor environment conditions have been worsening over the last 10-15 years.

The suggested temperature and humidity for decreasing the spread of viruses is within most existing regulations. However, the humidity of many indoor environments typically goes unchecked and frequently falls below 30%, per Quinn and Shaman (1).  Reisman and Das (2) shows that an increase of humidity in schools, from ordinary ~28% to ~45%, decreases influenza-like illnesses among children by 2.3 times in wintertime. Thus, increasing indoor humidity levels and temperatures, as stated above, would yield immediate benefits beyond just slowing the spread of COVID-19. These measures also seem to have no downsides, at least over a few weeks’ period.

There is no need to wait until summer or even mid-April. Hygrometers cost about $20 and humidifiers are also inexpensive.  In the absence of a humidifier, one can leave a pot of water simmering.

Immediate Recommendations

Inhibition of influenza viruses by environmental conditions is closest correlated with absolute humidity, per Shaman and Kohn (3). Absolute humidity is determined by relative humidity and temperature.

There is similarity of shedding, transmission, and infection mechanisms between the relevant corona- and Influenza viruses (Dormalen et al. (3), Iljaz (9), Prussin et al. (11), Pica and Bover (12)). That allows applying results from the previous studies of such viruses the COVID-19 epidemic. The previous studies (including Dormalen et al. (5), Noti (6), Iljaz (7), Yang and Marr (8)) are unanimous that increase in humidity sharply decreases transmission, survival, and infectivity of these viruses up to ~50% through multiple biological, chemical, and physical mechanisms. The positive effects are not so uniform above 50%, but the bottom line is that increase in humidity above 50% still restraints spread of the Influenza and coronaviruses. This said, SARS-CoV-2 and SARS-CoV have been described as relatively tough viruses.

These recommendations can be implemented by individuals in their homes as well as in their businesses.  However, to slow down the epidemics, they should be implemented by the whole community in the same time. Today, that means endorsement by governments.

The issue of low-quality indoor air might have been worsened recently. Energy conserving buildings are tightly sealed, have practically no passive ventilation, and often poor active ventilation. There is an energy conservation movement to keep wintertime indoor temperature at 68°F (20°C), and to drop temperatures even lower when the space is unoccupied.  Repeating this cycle dries out the air even more and creates ideal conditions for Influenza and coronaviruses to survive, stay infective, and even aerosolize. It is also beneficial for computer equipment to be kept at lower temperature and humidity levels.

The geography of the spread of COVID-19 seems compatible with the hypothesis that low-quality indoor environment is a large contributing factor.

Advanced Discussion

Important Analysis Factor

Comparing the COVID-19 spread in the West with that in Asia, like South Korea and Japan, there is one measure that has been undertaken in the East, but not in the West: contact tracing. Japan traced individual cases of COVID-19. In the US and EU, even anonymized infection tracing was not seriously considered. That might be the case due to Big Tech’s refusal to share their users’ location data with doctors and/or government agencies, even upon the user’s consent or request.

Beyond Humidity Levels of 50%-60%

The peer reviewed research indicates that corona- and Influenza viruses lose their viability outside of the human body with an increase in relative humidity even above 50%-60%. This begs the question: should indoor relative humidity recommendations, in the areas affected by the COVID-19 epidemic, be increased even higher, perhaps to 70-90%?

The ordinary recommendations for indoor humidity levels are between 40-60%. These recommendations balance different requirements. Even in hospitals, humidity is a balancing act, intended to minimize potential growth of viruses (higher RH inhibits enveloped RNA viruses), fungi (lower RH inhibits fungi), & bacteria (vary). However, when the dominant threat is a coronavirus, other concerns can put on the back burner for a few weeks, in order to slow this epidemic.

A humidity level of over 70% is uncomfortable for many and often develops an unpleasant smell. But we can tolerate these and other discomforts, for a few weeks, to fight the spread of COVID-19.

Other Indoor Climate Parameters

There is also an option to increase the temperature and/or relative humidity in spaces, when those spaces are unoccupied.  This could be done in office buildings at night and in residences during the day, when everyone is at work.

Increasing indoor ventilation may be the hardest indoor environmental recommendation to implement. Since not all windows (especially in commercial buildings) can be opened, non-traditional methods might be used. For example, where office windows cannot be opened, one might cut holes in them.

In many cases, it might be easier to use germ-killing air purification than to increase ventilation. See Ijaz (10) for air purification techniques.

Ozone generators should be re-considered. They kill germs in the air and on the surface.

Generally, there are many indoor parameters and measures that are not acceptable long term might be used for a few weeks in affected areas.

Aircrafts have very dry and cold air and a high density of passengers. They are not just virus carriers, but also incubators. (Based on Olsen (13), Booth (14).)

Notice that air cooling also decreases relative humidity. If this issue is not addressed, this epidemic might decrease in the late spring, then peak back in the summer due to elevated AC use.

Here, the term affected area is left to interpretation by the decision makers. It might include areas affected by the panic.

Annotated References

Peer Reviewed Studies

  1. Indoor temperature and humidity in New York City apartments during winter

Ashlinn Quinn, Jeffrey Shaman, Science of Total Environment, 2017

Levels of humidity seen here are consistent with increased influenza virus survival.

Mean indoor vapor pressure (a measure of absolute humidity) was 6.7 mb in the surveyed homes during the winter season.

This corresponds to RH=30% at 75°F.

2. Humidity as a non-pharmaceutical intervention for influenza A

Jennifer M. Reiman, Biswadeep Das, Center for Clinical and Translational Science, Mayo Clinic, PLOS ONE, 2018

There were 2.3 times as many ILI [influenza-like illness] cases in the control rooms compared to the humidified rooms, and whether there is a causal relationship, and its direction between the number of cases and levels of influenza virus in the rooms is not known. Additional research is required, but this is the first prospective study suggesting that exogenous humidification could serve as a scalable NPI for influenza or other viral outbreaks. …

This epidemiological correlation suggests that deliberate increases in AH could be a potential NPI to reduce the spread of influenza and other viruses. One approach is to maintain relative humidity (RH) between 40–60%, the proposed optimal range for reducing growth opportunities for viruses, bacteria, and fungi [15]. Our previous study, demonstrated that classroom humidification to RH of 40–60% may be a feasible approach to increase indoor AH to levels with the potential to reduce influenza virus survival (a target of 10mb) and transmission …

Elevated classroom humidification was maintained at an average of 9.89 mb in humidified rooms compared to 6.33 mb in control rooms

A grab bag of viruses. Control group relative humidity was 28%, while experimental groups achieved 42-45% humidity.

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

Neeltje van Doremalen, et all., National Institute of Allergy and Infectious Diseases, Azaibi Tamin, et all., CDC, The New England Journal of Medicine, 2020

We found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested [including various surfaces and aerosol]. This indicates that differences in the epidemiologic characteristics of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic.

4. Absolute humidity modulates influenza survival, transmission, and seasonality

Jeffrey Shaman (Columbia University) & Melvin Kohn (John Hopkins), Proceedings of the National Academy of Sciences, 2009

This paper summarizes the field: Absolute Humidity constraints Influenza Virus Transmission (IVT) and Influenza Virus Survival (IVS). The results are applicable to coronaviruses as well.

Previous studies indicate that relative humidity (RH) affects both influenza virus transmission (IVT) and influenza virus survival (IVS). Here, we reanalyze these data to explore the effects of absolute humidity on IVT and IVS. We find that absolute humidity (AH) constrains both transmission efficiency and IVS much more significantly than RH. In the studies presented, 50% of IVT variability and 90% of IVS variability are explained by AH, whereas, respectively, only 12% and 36% are explained by RH.

Includes physics of droplets: gravitation, speed, size, and evaporation. Cough droplets with viruses evaporate faster at lower humidity.  They also become smaller and stay airborne for a longer time. Absolute Humidity also better correlates with an increase in both temperature and relative humidity.

5. Stability of Middle East respiratory syndrome coronavirus (MERS-CoV) under different environmental conditions

N van Doremalen, T Bushmaker, V J Munster, Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Eurosurveillance, 2013

[Aerosolized] MERS-CoV decreased only 7% in viability at 40% RH, whereas the viability at 70% RH decreased significantly with 89% (unpaired one-tailed Student’s t-test, p=0.0045). The viability of A/Mexico/4108/2009 (H1N1) virus decreased under both conditions with 95% for 40% RH and 62% for 70% RH respectively

MERS-CoV was very stable in aerosol form at 20°C – 40% RH. The decrease in viability at 20°C – 70% RH (89%) was comparable to that of A/Mexico/4108/2009 (H1N1) virus. Severe acute respiratory syndrome coronavirus (SARS-CoV) has been reported to stay viable for up to five days at 22 to 25°C and 40 to 50% RH and increase in temperature and humidity resulted in a rapid loss of viability [19]. Although a comparison between different experimental studies should be approached cautiously, the relative stability of MERSCoV at 20°C – 40% RH and the rapid decrease in virus viability at higher temperatures and higher humidity suggests that MERS-CoV and SARS-CoV share relatively similar stability characteristics.

Suggests that coronaviruses are more sensitive to humidity than influenza viruses. This applies to aerosol forms as well as to surface born (fomite).

6. High humidity leads to loss of infectious influenza virus from simulated coughs

John D. Noti,  Health Effects Laboratory Division (HELD), National Institute for Occupational Safety and Health (NIOSH), Centers for Disease Control and Prevention (CDC), PLOS ONE, 2013,  Included into CDC NIOSHTIC-2, 2013

Total virus collected for 60 minutes retained 70.6–77.3% infectivity at relative humidity ≤23% but only 14.6–22.2% at relative humidity ≥43%. Analysis of the individual aerosol fractions showed a similar loss in infectivity among the fractions. Time interval analysis showed that most of the loss in infectivity within each aerosol fraction occurred 0–15 minutes after coughing.

Maintaining indoor relative humidity >40% will significantly reduce the infectivity of aerosolized virus.

Loss of infectivity is only one of the effects that decrease transmission. The infectivity is at a minimum at RH=43% (here, rounded up to 50%), then slightly increases and then drops again at RH>70%

The effect of increasing humidity on viral survival differed among several reported studies as Hemmes et al. [3], Hood [4] and Harper [5] concluded that survival was maximum at 10–25% RH and minimal at high >50% RH whereas, Shechmeister [6] and Shaffer et al. [7] found survival was maximal at 20–25% RH, minimal at 50% RH, and moderate at 70–80% RH.

7. Survival Characteristics of Airborne Human Coronavirus 229E

M. K. Ijaz, Journal of General Virology, Society for General Microbiology, 1985

The survival of airborne human coronavirus 229E (HCV/229E) was studied under different conditions … High RH [=80%] at 20 °C, on the other hand, was found to be the least favourable to the survival of aerosolized virus and under these conditions the virus half-life was only about 3 h;

8. Dynamics of Airborne Influenza A Viruses Indoors and Dependence on Humidity

Wan Yang & Linsey C. Marr, Virginia Tech, PLOS ONE, 2011

… we further model the dynamics of droplets emitted from a cough in an indoor environment and illustrate the evolution of infectious IAV [influenza A viruses] concentrations and size distributions, considering removal by gravitational settling, ventilation, and viral inactivation. We are thus able to determine the magnitude by which humidity affects airborne concentrations of infectious IAVs. … Higher RH favors removal of infectious IAVs. 

Maintaining a high indoor RH and ventilation rate may help reduce chances of IAV infection.

9. The Effects of Temperature and Relative Humidity on the Viability of the SARS Coronavirus

K. H. Chan, et all., University of Hong Kong, Hindawi – Advances in Virology, 2011

Interestingly, during the outbreak of SARS in Guangzhou, clinicians kept the windows of patient rooms open and well ventilated and these may well have reduced virus survival and this reduced nosocomial transmission. SARS CoV can retain its infectivity up to 2 weeks at low temperature and low humidity environment

Our studies indicate that SCoV is relatively more stable than the human coronaviruses 229E or OC43 … SARS CoV can survive at least two weeks after drying at temperature and humidity conditions found in an air-conditioned environment.

This is applicable to SARS-CoV dried in cold dry office conditions.

10. Generic aspects of the airborne spread of human pathogens indoors and emerging air decontamination technologies

M. Khalid Ijaz, et all, American Journal of Infection Control, 2016

Environmental factor Viruses
Temperature As temperature increases, survival decreases DNA viruses are more stable than RNA viruses at higher temperatures
RH Enveloped viruses (most respiratory viruses, influenza) survive longer at lower RH (20%-30%) Nonenveloped viruses (adenovirus, rhinovirus, and polio virus) survive longer in higher RH (70%-90%)
Atmospheric gases Ozone inactivates airborne viruses to a greater degree than bacteria or fungi
Light and irradiation UV light is harmful (RH-dependent)

And

Table 3 Current and emerging technologies for decontamination of indoor air for human pathogens
Technology Description Pathogen tested Remarks
UV irradiation Upper-room 254 nm UVC light UV light (254 nm) at 3 levels of RH Influenza A virus (H1N1, PR-8) Virus susceptibility to UV increased with decreasing RH
UV light (254 nm) … a coronavirus as surrogate for SARS, … High RH did not protect viral aerosols
Ozone generator Gaseous ozone and aerosolized virus were generated continuously into the chamber Bacteriophages: single-strand RNA [like influenza & coronaviruses] and DNA, double-strand RNA and DNA 95% of virus aerosol was <2.1 µm in diameter Viruses were more susceptible to ozone at higher RH

11. Survival of the Enveloped Virus Phi6 in Droplets as a Function of Relative Humidity, Absolute Humidity, and Temperature

Aaron J. Prussin, II, et all., American Society of Microbiology, Applied and Environmental Microbiology, 2018

Shaman and Kohn (12) have concluded that the relationship is stronger with AH than with RH. According to their analysis of virus survival in aerosols (24) and transmission in guinea pigs (16), AH explains 50% and 90% of the variability in influenza virus transmission and survival, respectively … In a study examining influenza virus survival in droplets at elevated temperatures (55 to 65°C), McDevitt et al. (27) also reported that AH is a better predictor than RH for virus inactivation. …

Due to the challenges and biosafety concerns of working with the influenza virus and coronavirus, this study employed the enveloped bacteriophage Phi6, which has been suggested as a surrogate for the influenza virus (31, 32) and SARS coronavirus (33). Our results provide novel information about the complex interplay between temperature, humidity, and the survival of viruses in droplets.

Shows optimum humidity levels at 75-80% and temperature above 25 degrees Celsius.

12. Environmental factors affecting the transmission of respiratory viruses

Natalie Pica, Nicole M Bouvier, Mount Sinai School of Medicine, Science Direct, 2012

► Respiratory viruses are spread from person to person via various modes of transmission, including direct and indirect contact, droplet spray, and aerosol

Modes of person-to-person transmission of respiratory viruses

Contact transmission In both modes of contract transmission (direct and indirect), contaminated hands play an important role in carrying virus to mucous membranes.
Direct transmission Virus is transferred by contact from an infected person to another person without a contaminated intermediate object (fomite).
Indirect transmission Virus is transferred by contact with a contaminated intermediate object (fomite).
Droplet spray transmission Virus transmits through the air by droplet sprays (such as those produced by coughing or sneezing); a key feature is deposition of droplets by impaction on exposed mucous membranes.
Aerosol transmission Virus transmits through the air by aerosols in the inspirable size range or smaller; aerosol particles are small enough to be inhaled into the oronasopharynx and distally into the trachea and lung.

(Adapted from Centers for Disease Control and Prevention (CDC); URL: http://www.cdc.gov/influenzatransmissionworkshop2010/).

Also

airborne routes (droplet spray and aerosol) seemed to be more important in SARS coronavirus spread

And

Influenza viruses Orthomyxoviridae Contact, droplet spray and/or aerosol (conflicting data)
SARS coronavirus Coronaviridae Droplet spray and aerosol, possibly contact

In the early 1960s, Schulman and Kilbourne developed an influenza virus transmission model in mice. Although mouse-to-mouse transmission is relatively inefficient, they still observed a significant decrease in transmission efficiency with increasing relative humidity (RH) …

Transmission of viruses via airborne routes may be affected by ambient humidity, which affects not only the virus’ stability but also respiratory droplet size, as water content evaporates. In turn, droplet size influences whether the particle will quickly settle to the ground or remain airborne long enough to be inhaled into the respiratory tract of a susceptible host. For influenza virus, mathematical modeling suggests that RH is an important variable in airborne transmission of influenza virus; high RH favors removal of infectious particles both by increasing the settling of large, water-laden droplets and by hastening virus inactivation

13. Transmission of the Severe Acute Respiratory Syndrome on Aircraft

Sonja J. Olsen, Ph.D., The New England Journal of Medicine, 2003

This paper suggests that aircraft might be not only carriers, but incubators of the coronaviruses because of the human density and low humidity levels.

14. Detection of Airborne Severe Acute Respiratory Syndrome (SARS) Coronavirus and Environmental Contamination in SARS Outbreak Units

Timothy F. Booth, et all, Oxford Journal of Infectious Disease, 2005

Previous studies of human coronavirus 229E (a common cold virus) showed that experimental aerosols could persist and retain viability for as long as 6 days at 20C and 50% relative humidity [20]. These conditions are representative of typical indoor environments. Although such experiments may overestimate the ability of a virus to survive in real environments (for example, they do not take into account air turnover rates in buildings), one would expect SARS CoV to have similar airborne survival characteristics, given that these viruses are in the same family and have broadly similar physicochemical properties

Popular Medical Advice

This Inexpensive Action Lowers Hospital Infections And Protects Against Flu Season

Leah Binder, Forbes, 2019

Since that study was published, there is now more research in peer-reviewed literature observing a link between dry air and viral infections, such as the flu, colds and measles, as well as many bacterial infections, and the National Institutes of Health (NIH) is funding more research. Taylor finds one of the most interesting studies from a team at the Mayo Clinic, which humidified half of the classrooms in a preschool and left the other half alone over three months during the winter. Influenza-related absenteeism in the humidified classrooms was two-thirds lower than in the standard classrooms—a dramatic difference.

How humidity could help fight coronavirus

Emily Bamforth, Cleveland.com, 2020

Humidity could be helpful in relieving the symptoms of coronavirus, as well as preventing it from spreading

Just Dumb

New York City Health, Frequently Asked Questions (FAQs) for Residential Buildings Coronavirus Disease (COVID-19)

Should temperature or humidity in buildings be adjusted to prevent the transmission of COVID-19? • There is no data to suggest that adjusting the temperature or humidity of a building would be an effective way to reduce transmission of COVID-19. The Health Department does not recommend that buildings increase humidity levels to control COVID-19 transmission.

Such obscurantism might have contributed to New York becoming the new COVID-19 epicenter. New York and New Jersey have more than half of the 68,581 COVID-19 cases, confirmed in the US by March 26, 2020.

Conflict of Interest Statement

The Author declares absence of conflicts of interest.


Note from Anthony: I’ve been sick myself the last few days, but I can’t tell if it was flu or seasonal allergy issues, or COVID-19. Time will tell.

What I can tell you though, is that I got one of these, and it has helped my sneezing and coughing. It has a UV-C light to kill germs, and that type of UV light may kill the Coronavirus according to this article.

There are also models that add heat and humidity to the indoor air:

As suggested in the article above by Leo Goldstein, there may be value against COVID-19 in increased humidity, increased temperature, and use of UV-C light in a circulating air filter

Best of luck in these trying times to all!

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March 28, 2020 4:20 pm

New Orleans is an emerging “hot spot.” New Orleans has high humidity. Guess that sort of proves that humidity isn’t going to help you.

Scissor
Reply to  Henry Pool
March 28, 2020 5:19 pm

It could always have been worse without the humidity.

Stevek
Reply to  Henry Pool
March 28, 2020 5:50 pm

Temperature and Humidity are just one factor. New Orleans is having a problem due to the Mardi Gras which packed thousands of people close together.

https://www.google.com/amp/s/www.nytimes.com/2020/03/26/us/coronavirus-louisiana-new-orleans.amp.html

Greg
Reply to  Stevek
March 28, 2020 8:15 pm

Mardi Gras lasts all week and Louisiana RH is high in the morning but intermediate in pm and evening.

Indoor areas are still heated and thus low RH.

simplistic on-size-fits-all statements do not provide any insight.

Tom in Florida
Reply to  Henry Pool
March 28, 2020 6:48 pm

Humidity cannot overcome places that are sh*t holes.

Paul C
March 28, 2020 4:37 pm

My personal theory on biocidal radiation deactivating airborne virus is that the once common cathode ray tube TVs and monitors which emitted small doses (primarily at switching on/off) of low-powered x-ray (next in spectrum to UV-C) provided a low level of protection which is now absent. If damp killed the flu, the UK wouldn’t have a flu season.

March 28, 2020 4:37 pm

Fearless Leader wants to shut down NYC/NJ/CT, and open up the rest of the country by Easter. He needs to make up his mind.

Josh Postema
Reply to  Henry Pool
March 28, 2020 5:41 pm

Why should do very place be treated identically? My county has had 22 cases total and none new in over a week. Why should we be held home indefinitely because New York keeps getting new cases?

Reply to  Josh Postema
March 28, 2020 6:13 pm

Because it’s not just NYC. It’s Chicago, Detroit, Atlanta, Seattle, New Orleans, LA and many other cities.

Bindidon
March 28, 2020 4:58 pm

rud istvan

The three things to do are: social distancing (protect from cough), wash hands frequently, since little alcohol sanitizer is available, and don’t touch your face unless right after hand washing.

Yes: That is the MAJOR RULE to follow!

Thanks for having the energy to repeat this all the time.

The rule you mention probably is 1,000 times more important than the entire guest post.

We could add: all governments worldwide should oblige the supermarkets to protect their cashiers by installing a simple glass panel separating them from possibly infected clients.

Rgds
J.-P. D.

Greg
Reply to  Leo Goldstein
March 28, 2020 7:47 pm

Until a few weeks ago hand sanitiser was soap.

The new fad for hand sanitiser seems to give folks the impression it is better than soap : hey , it’s specialise product, must be good.

hand sanitiser is for when you don’t have access to soap and water ( like carry it in your bag ).

Soap (~pH 9) is quite alkaline and destroys the virion’s lipid protective sheath. Better than washing up liquid (~pH 8)

Our local supermarket ( Fr ) set up plexiglass shields at each till last week.

Greg
Reply to  Leo Goldstein
March 28, 2020 8:33 pm

Leo, great article in general. I have been saying RH is a key factor in seasonal illness for years. I am really minimalist in heating my living area and I don’t get ill. The average Joe who lives in 22-25 deg C at home is always catching colds and flu.

You seem to confuse absolute humidity and RH in saying a/c reduces RH. a/c causes condensation in the heat exchanger because RH reaches 100% and condensations occurs.

Is the problem that the air them warms again, dropping RH? One problem is an over powered a/c will not run long enough to reduce RH. I don’t see indications it will lower it too much.

A couple of people have picked up on this. Can you comment ?
https://wattsupwiththat.com/2020/03/28/increased-indoor-humidity-may-decrease-coronavirus-covid-19-transmission/#comment-2949720

Greg
Reply to  Leo Goldstein
March 29, 2020 2:29 pm

thanks for the reply.

“but we agree that a/c reduces RH through condensation.”

No, we don’t agree ! a/c reduces AH of incoming air through condensation. Condensation happens because RH is near 100%, not because it is low. So air entering via a/c unit is likely to be very high. This RH may drop as it mixes with warmer air already inside but that implies increasing the RH of the air already inside.

I really don’t see any supporting argument for how a/c reduced RH

u.k.(us)
March 28, 2020 5:15 pm

Take long boiling hot showers, breathe deeply the humidity.
Eat enough to keep your natural defense mechanisms at fighting strength.
Vitamins ??
Then just “damn the torpedoes”.

Greg
Reply to  u.k.(us)
March 28, 2020 7:27 pm

A shower will not raise your body temperature. You’ll just burn your skin.

An hour long hot bath may do some good and help you sweat out any infection. But sadly baths are a bourgeois luxury these days.

Greg
Reply to  Greg
March 28, 2020 7:54 pm

If you want to breathe water vapour use a pot of hot water and an towel .

Roger Knights
Reply to  Greg
March 28, 2020 8:23 pm

“If you want to breathe water vapour use a pot of hot water and an towel.”

Or a humidifier.

GERARD STRINGER
Reply to  u.k.(us)
April 8, 2020 2:18 pm

Absolutely! Each day’s morning routine should start with an Amazon rain-forest shower. Purchase a small temp/humidity meter, (Walmart sells one for about 12 bucks).Bring the meter into the shower. Shower in hot water, keep the temp stable by increasing the hot water as it cools. Stay in there, breathing the humidity and monitoring the levels of heat and humidity for 15-20 mins. Ideally, when finished, both should read in the eighties. This AM, mine read 84 for both. After water is shut off, towel off in the shower.
Remember to breath deeply through nose and mouth. Even if the bath has a fan, be prepared to wipe down the walls, it’s gonna be hot with lots of moisture. Covid -19 is a respiratory disease. It doesn’t like heat&humidity. This may be effective. Beats the hell out of doing nothing!

Greg
March 28, 2020 6:12 pm

There is no need to wait until summer or even mid-April. Hygrometers cost about $20 and humidifiers are also inexpensive. In the absence of a humidifier, one can leave a pot of water simmering.

There one other way to achieve a similar result TURN THE HEATING DOWN.

Apparently this is so abhorrent that it does not even occur to the author to mention this possibility.

Reply to  Greg
March 29, 2020 2:37 am

There is no actual evidence that changing the temp or RH in our homes will have any effect at all.

Greg
Reply to  Leo Goldstein
March 29, 2020 2:41 pm

Reisman and Das (2) shows that an increase of humidity in schools, from ordinary ~28% to ~45%, decreases influenza-like illnesses among children by 2.3 times in wintertime.

You were amiss in not clearly specifying it in the article but this is RH not AH.

The peer reviewed research indicates that corona- and Influenza viruses lose their viability outside of the human body with an increase in *relative humidity* even above 50%-60%.

9. The Effects of Temperature and Relative Humidity on the Viability of the SARS Coronavirus
K. H. Chan, et all., University of Hong Kong, Hindawi

BTW that’s “et al” not et all , a mistake you make consistently 😉

Enveloped viruses (most respiratory viruses, influenza) survive longer at lower RH (20%-30%)

There does not seem to be any doubt we are talking about RH here not AH. Thanks for bringing up a very important subject. It’s a shame you don’t seem to have understood it yourself and made the a/c blooper.

Tom in Florida
March 28, 2020 6:46 pm

Do not forget to get the correct a/c filter. A MERV 13 rated filter will trap virus. Anything less and you are just recirculating the virus throughout your home. Most home a/c filters are rated for 90 days however I am changing mine every 30 days. Maybe over cautious but the cost is low enough not to matter.

Stevek
Reply to  Tom in Florida
March 28, 2020 7:12 pm

My HVAC guy was trying to sell us on a UV light thing that supposedly kills bacteria in the air, it attaches to system so air goes through the light. I’m not sure though if it would do anything.

Tom in Florida
Reply to  Stevek
March 29, 2020 4:58 am

UV lights are proven to work however there are two kinds. The most common is used to prevent mold and mildew on the coils, all good units have these. The other is more expensive and is used to kill living organisms as the air passes by in the return duct. This type is usually an optional add on. Your specific circumstances would dictate if it is worth the extra expense and maintenance cost.

Reply to  Stevek
March 29, 2020 9:55 am

I have a UV light system on my HVAC, will definitely kill viruses in the air, it’s UVC. Installed initially for mold (100+yo house)

March 28, 2020 7:17 pm

According to the Business Insider, people over 75 are almost 100 times more likely to die than people 18-44. For some reason I cannot post the graphic here, but, this tells me that destroying our economy is not a good idea.

Let the young and strong go back to work. They get infected, they get better, we do not put 25 million people into unemployment for a risk of 0.17% of death.

This is a flu/cold that is very hard on old sick people. The Great Depression was very hard on old sick people, and Everyone Else Too!

Greg
Reply to  Michael Moon
March 28, 2020 7:51 pm

0.17% of 25 million is still a lot people before you get herd immunity at 60-70% but I agree shutting down the whole damned country is crazy and likely to do more damage to lives than the damned virus.

Reply to  Michael Moon
March 29, 2020 2:35 am

The binary lived/died question is not the whole story.
Many people who ultimately live only survive after several weeks in a hospital with viral pneumonia.

I am not saying the shutdown is justified or a good idea…but it did not happen simply because some very old people or people who were on their deathbed anyway, were/are going to die.
There is far more to this story than that.

A C Osborn
Reply to  Michael Moon
March 29, 2020 4:12 am

0.17%, I have no idea where you get that value from, but whatever the actual number is you can at least double it for all the non COVID deaths that will occur due to health system oveload.
Unless you are advocating not bothering to treat critical COVID patients at all?

fah
March 28, 2020 9:32 pm

The air purifier you bought does have one admirable feature: “A washable AOC Carbon Filter”

Wonderful ridding your life of nuisance AOC.

Greg
Reply to  fah
March 29, 2020 4:11 am

I’ve ordered one. I’m going to put it between the decoder and the screen.

March 29, 2020 12:22 am

Yes, & original post about humidity should be expanded to include the following, at least for influenza viral infections in the research cited below.

In lungs under low humidity there is less activation of Type 1 Interferon & it’s subsequent induction of 100s of interferon influenced genes. Then the unchecked virus is able to stimulate activity of capsase enzymes which in physiological pathways contribute to “… lung pathology & mortality, due to formation of neutrophil extra-cellular traps ….”

As per (2019) report “Low ambient humidity impairs barrier function and innate resistance against influenza infection”; free full text availableon-line.

mwhite
March 29, 2020 2:21 am

“Videos have emerged of desperate people in Italy begging for help because they have run out of money and food.”

https://www.msn.com/en-gb/news/coronavirus/italy-becoming-impatient-with-lockdown-and-social-unrest-is-brewing/ar-BB11QFkh

A taste of things to come?

Greg
Reply to  mwhite
March 29, 2020 8:23 am

Looking at France after 14 days of restrictions, there is mild improvement in doubling time of new infections but it started at least 2 days BEFORE they came into effect whereas any attribution of this improvement to restricted movement would need typically 5 days incubation to show up.

comment image

Are we destroying the economy for nothing ??

A C Osborn
Reply to  Greg
March 29, 2020 8:53 am

The total lockdown started on the 17th, 12 days ago.
The reason that you won’t see much change in the new cases ROC is because there are thousands of undetected cases that are already in the system but not tested, probably self isolating.
New cases = those found by new tests not people newly infected with the virus.

Greg
Reply to  A C Osborn
March 29, 2020 9:46 am

Yes, all these stats hide the true number of cases, with mild or symptom-less cases wisely staying well clear of any hospitals and being told not to go to doctors surgeries.

Obviously there is a sampling bias. Are you saying that the sampling bias has changed in the last 12d in a way which is masking a real change in the rate of contagion?

do you have any evidence for that opinion or is it just total speculation?

A C Osborn
Reply to  Greg
March 29, 2020 11:28 am

We don’t know, we don’t know any changes in sampling rates, whe they were tested before the results come back, who is being sampled, how well the people are adhering to the new regs etc.
So it is a considered opinion based on what has been going on.

Greg
Reply to  Greg
March 29, 2020 2:54 pm

So you are agreed that there is no evidence that the shutdown has any measureable effect on contagion. Absence of proof is not proof of absence, but the point I was making is that the data ( cr4ppy as it may be ) does not show any attributable effect.

Since this is the data they are feeding us as proof of the “pandemic” it’s all we have to go on.

If they provided concurrent data on how many tests had been conducted maybe we would have more to work on. We could tell whether they arranged the clamp down announcements to coincide with the day after they had provided 100k new test kits in the hospital system.

The paucity of the data provided is lamentable at a time when they are requiring public cooperation with drastic measures and destroying the economy.

No wonder the arab ‘banlieusards” are giving them the finger.

Reply to  Greg
March 30, 2020 5:45 am

I know if I stay away from other people as much as possible, I have a reduced chance of being exposed.
As does everyone.
If I stay inside, there is no chance I get infected unless someone or something with virus comes into my house.
No one knows who has it, and everyone that has it can spread it to an unlimited amount of people they encounter.
I have never been worried about getting sick, but in this case, I have come to the conclusion I really do not want to get it and wind up with viral pneumonia.
Average time on a respirator is over 4 weeks for the people who are winding up needing one.

Vuk
March 29, 2020 4:19 am

Quote from Sputnik News:
“The Russian Federal Agency for Biomedicine has made a preparation for the treatment of coronaviruses based on the antimalarial drug mefloquine, according to the press service of the organization. This preparation blocks the cytopathological effects of coronavirus at the cellular level and stops its multiplication, it is said. In addition, the immunosuppressive effect of mefloquine blocks any inflammation that occurs after a person is infected.”

john
March 29, 2020 5:59 am

Mold can be a pretty serious issue. It likes humidity at 50% and higher.

https://www.epa.gov/mold/mold-course-chapter-2#Chapter2Lesson3

Humidity at 30% helps with pests like dust mites/ cock roaches.

I see UV lights installed at various entry ways at hospitals, nursing homes and retirement facilities.

Good cleaning/sanitation is a must.

Bill Parsons
Reply to  john
March 29, 2020 12:17 pm

Our local library locations shut down along with the book drops and offices. Borrow times have been extended and all fines waived.

I wondered what measures they might be taking to disinfect all that paper which was circulating through the public’s hands up until a mid-March, but it appears their strategy is to stop physical material from circulating until they can surmise that the majority of the virus is kaput… four to five days after the apocalypse.

john
March 29, 2020 6:13 am

If they shut down non vital interstate traffic in NY, NJ, CT, RI plus MA, they would essentially stop the virus AND DRUG TRADE in the NE region at the source.

The cartels would try to adapt but that would only identify who’s doing it via all that electronic monitoring going on.

EMS is already stretched for OD calls and now this…

2 birds one stone.

Greg
Reply to  john
March 29, 2020 8:26 am

but then when people start sweating and shivering they will not know whether it’s cold turkey or COVID.

Rich
March 29, 2020 11:17 am

What happens if your house has very dry air because of forced hot air heat?
10-20% RH at 70F

34% right now only because it’s raining outside

Carlie Coats
Reply to  Rich
April 1, 2020 5:46 am

I have two of these Honeywell wick-style humidifiers, and they keep my (2500 sq ft) in-house humidity at least 45% even in mid-winter (sometimes evaporating as much as 15 gal of water per day). Note that they have a design whereby air is forced through a wetted wick, and so do not create aerosol droplets that evaporate (leaving a solid-core fine dust); in fact, they probably filter out some indoor air pollution.

https://smile.amazon.com/Honeywell-Cool-Moisture-Console-Humidifier/dp/B000G0LDRI/ref=sr_1_18?crid=1U7WME65G0YN9&keywords=honeywell+humidifier&qid=1585744860&sprefix=honeywell+%2Caps%2C168&sr=8-18

March 30, 2020 5:39 am

Masks.
It is so obvious.
There are decades of studies proving the value of barrier protection.
It is not a magic bullet, it is another layer of protection…and a very effective one if the right mask is worn:

https://medium.com/@Cancerwarrior/covid-19-why-we-should-all-wear-masks-there-is-new-scientific-rationale-280e08ceee71

“Great explanation of why simple masks (ie. not N95) are so effective at stopping #COVID19 and why the continuing silence of medical leaders in US/Canada is baffling”

https://twitter.com/drjasonfung/status/1244478421478133760?s=20

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