Increase Indoor Humidity

To reduce transmission of COVID-19 indoors: increase indoor humidity (and, possibly) temperature.

If you are in an affected area, you set the indoor temperature to 75°F (24°C) or more, and relative humidity to 50-60%. The humidity is more important parameter. In the same time, keep the space well ventilated. See Increased indoor humidity may decrease #Coronavirus #COVID-19 transmission in WUWT.

Medical Sources:

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

Study: Humidifiers May Help Fight Flu
The finding also suggests that using a humidifier may be a good idea in places where the spread of influenza poses a serious threat …

High Humidity Leads to Loss of Infectious Influenza Virus from Simulated Coughs [found on]

Modeling the airborne survival of influenza virus in a residential setting: the impacts of home humidification

Laboratory research studies indicate that aerosolized influenza viruses survive for longer periods at low relative humidity (RH) conditions. Further analysis has shown that absolute humidity (AH) may be an improved predictor of virus survival in the environment. Maintaining airborne moisture levels that reduce survival of the virus in the air and on surfaces could be another tool for managing public health risks of influenza.

General Media:

Humidity helps in the fight against COVID-19, virologists report

low ambient humidity hurts the ability of the immune system to fight respiratory viral infection

Consumer Reports recommends humidifiers to decrease flu-like virus transmission.


By raising indoor relative humidity levels to 43 percent or above [here, 75% is recommended], investigators reported that they were able to quickly render 86 percent of airborne virus particles powerless.

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

Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature

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.

CDC: Common Human Coronaviruses

[not specific to COVID-19]

There is no vaccine to protect you against human coronaviruses and there are no specific treatments for illnesses caused by human coronaviruses. Most people with common human coronavirus illness will recover on their own. However, to relieve your symptoms you can:

    • take pain and fever medications (Caution: do not give aspirin to children)
    • use a room humidifier or take a hot shower to help ease
    • a sore throat and cough
    • drink plenty of liquids
    • stay home and rest

If you are concerned about your symptoms, contact your healthcare provider.

“germs may be able to survive in the drier air conditions. So the thought is that, if you keep the humidity level up in a room, the virus is less likely to survive.”

“influenza virus transmission and stability, have identified absolute humidity and temperature as climatic predictors of influenza epidemics in temperate regions of the world”

“Breathing dry air can cause respiratory ailments such as asthma, bronchitis, sinusitis and nosebleeds. “The mucus that normally should be gooey and thick and can trap infection gets drier. So you’re more likely to get a cold because your mucus is not as able to catch things that you breathe in.”

Notice that this study was done on SARS-CoV, NOT on SARS-CoV2, the COVID-19 virus.

In this study, we showed that high temperature at high relative humidity has a synergistic effect on inactivation of SARS CoV viability while lower temperatures and low humidity support prolonged survival of virus on contaminated surfaces. The environmental conditions of countries such as Malaysia, Indonesia, and Thailand are thus not conducive to the prolonged survival of the virus. In countries such as Singapore and Hong Kong where there is a intensive use of air-conditioning, transmission largely occurred in well-air-conditioned environments such as hospitals or hotels.

Originally published on 2020-03-19. Updated on March 21-25, Apr 1.

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