Using a humidifier can reduce the chances of contracting COVID-19

Respiratory viruses love winter. These pathogens thrive in the cold and travel more easily from host to host in dry air.

“When cold outdoor air with little moisture is heated indoors, the relative humidity drops to about 20 percent,” Akiko Iwasaki, an immunobiologist at Yale University, said in a statement.

“This dry air provides a clear path for viruses in the air.”

Relative humidity (RH) is a measure of air saturation with water vapor. So, in a room with 40 percent relative humidity, the air holds 40 percent of the total amount of moisture it could hold in total.

The drier the air, the lower the relative humidity, and the easier it is for viruses, including coronavirus, to spread.

That’s why Linsey Marr, an aerosol researcher at the University of Virginia Tech, who studies coronavirus transmission, recommends using a humidifier in your home.

“You could invest in a humidifier and set it to keep humidity above 40, but below 60 percent in winter,” she told Business Insider. “The virus doesn’t survive well in these conditions, and your immune response works better than when the air is dry.”

Humidity and temperature affect the spread of the coronavirus

Studies show that coronavirus spreads more easily when temperatures and humidity are low.

A July analysis by aerosol research scientist Ajit Ahlawat and his colleagues found that the chances of airborne transmission of coronavirus in dry places are higher than in wet areas.

This is because coronavirus particles in drier, less humid air absorb less moisture and therefore stay worse for longer. This makes them more likely to be inhaled and infect someone new.

In addition, coronavirus particles become more stable as temperatures and humidity levels decrease, helping them to remain stable enough to infect a new host when they arrive.

Moreover, like the flu, the coronavirus is located in a fatty layer called the lipid envelope that helps it survive the journey from one person to another. This mantle dries faster at higher temperatures.

Humid air can also act against the protective layer, creating havoc on the structure of the lipid envelope, deactivating the virus.

“To control airborne transmission of coronavirus indoors, especially in poorly ventilated indoor locations such as certain hospitals, schools and public buildings, we recommend the use of humidifiers,” Ahlawat told Business Insider.

Like Marr, he recommends indoor humidity between 40 and 60 percent.

Higher temperatures can also prevent the virus from spreading to surfaces, although this type of transmission is rare.

A study published in June found that warmer weather conditions could reduce how long the coronavirus survives on surfaces.

40 to 60 percent of relative humidity also benefits our immune system

This fall, Iwasaki helped launch a petition calling on the World Health Organization to set guidelines for indoor humidity levels. RH calls 40-60 percent relative humidity a “sweet spot” because indoor air in that range “allows the nose and throat to maintain strong immune responses” against many viruses.

Built-in protections of our immune system – like mucus in the nose – work better when the air is more humid.

This is because the mucus coats flexible hair-like appendages called cilia that protrude from the cells of our airways (imagine them as a seaweed swaying underwater). Cilia has the task of catching viral particles trying to float into our lungs.

According to a recent study by Iwasaki and her colleagues, low humidity dries out that mucus; as the lubricating mucosa dries, these protective cilia fall flat, interfering with their ability to capture the virus.

But experts warn of too much moisture

However, it is crucial not to overdo it with moisture.

“Be very careful not to exceed 65 percent because it can boost mold growth,” Marr said. The resulting mold can trigger asthma, and many people are allergic to slow mold.

Ahlawat also said a humidity level of over 60 per cent “would be too uncomfortable for indoor residents”.

Numbers aside, some experts are against the use of humidifiers in general as a means of reducing viral transmission.

“This is an unproven approach and has the potential for very bad side effects,” Donald Milton, a professor of the environment at the University of Maryland, told Elemental in November. “I don’t recommend it.”

Marr also warned that the use of humidifiers should not be considered a drug to stop the spread of the virus.

“The most important thing is to wear a mask, maintain distance, ensure good ventilation and / or air filtration, and wash your hands,” she said.

This article was originally published by Business Insider.

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