Scientists recommend at least 40% humidity in public buildings to curb COVID-19 spread
New Delhi: In addition to measures like social distancing and wearing masks, an Indian-German team of scientists recommend controlling indoor humidity conditions to contain the spread of the novel coronavirus which causes COVID-19.
The researchers, including those from CSIR National Physical Laboratory in New Delhi, said in order to contain the pandemic, it is extremely important to implement standards for indoor air humidity in rooms with many people, such as hospitals, open-plan offices, or public transport.
In their review of studies, published in the journal Aerosol and Air Quality Research, the scientists specifically drew focus on relative humidity, which is a measure of water vapour in the air compared to the total saturation of vapour that can exist in the air at its current temperature.
According to the study, a relative humidity of 40 to 60 percent could reduce the spread of viruses and their absorption through the nasal mucous membrane.
The scientists said tiny drops of five micrometres in diameter, such as those produced when speaking, can float in the air for up to nine minutes.
"In aerosol research, it has long been known that air humidity plays a major role -- The more humid the air is, the more water adheres to the particles and so they can grow faster. So, we were curious -- what studies have already been conducted on this," explained Ajit Ahlawat, a co-author of the study from the Leibniz Institute for Tropospheric Research (TROPOS) in Germany.
According to the scientists, humidity affects the behaviour of microorganisms within the virus droplets, and the survival or inactivation of the virus on the surfaces.
They said it also influences the role of dry indoor air in the airborne transmission of viruses.
"If the relative humidity of indoor air is below 40 per cent, the particles emitted by infected people absorb less water, remain lighter, fly further through the room and are more likely to be inhaled by healthy people," Ahlawat explained.
"In addition, dry air also makes the mucous membranes in our noses dry and more permeable to viruses," he said.
The scientists believe the new findings are particularly important for the upcoming winter season in the northern hemisphere, when millions of people will be staying in heated rooms.
"Heating the fresh air also ensures that it dries. In cold and temperate climate zones, therefore, the indoor climate is usually very dry during the heating season. This could encourage the spread of coronaviruses," said study co-author Alfred Wiedensohler of TROPOS.
At a higher humidity, the scientists said droplets grow faster, fall to the ground earlier, and can be inhaled less by healthy people.
"A humidity level of at least 40 per cent in public buildings and local transport would therefore not only reduce the effects of COVID-19, but also of other viral diseases such as seasonal flu. Authorities should include the humidity factor in future indoor guidelines," added study co-author Sumit Kumar Mishra of CSIR - National Physical Laboratory in New Delhi.
For countries in cool climates, the scientists recommend a minimum indoor humidity.
They said countries in tropical and hot climates, on the other hand, should take care that indoor rooms are not extremely undercooled by air conditioning systems.
When air is extremely cooled, it dries out the air and the particles in it, making people inside the room feel comfortable, but the dry particles will remain in the air for longer duration, the researchers warned.
They added that the measures already known, such as social distancing, having as few people per room as possible, and wearing masks should also be practised to lower the risk of infection.
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Unemployment is biggest problem faced by youth, it is directly linked to 'vote chori': Rahul Gandhi
New Delhi (PTI): Congress leader Rahul Gandhi on Tuesday claimed that as long as elections are "stolen", unemployment and corruption will continue to rise, and asserted that young people will no longer tolerate "job theft" and "vote theft".
In a post on X in Hindi, the Leader of Opposition in the Lok Sabha said unemployment is the biggest problem facing youth in India and it is directly linked to "vote chori".
When a government wins public trust and comes to power, its first duty is to provide employment and opportunities to the youth, he said.
"But the BJP doesn't win elections honestly -- they stay in power by stealing votes and controlling institutions," Gandhi alleged.
That's why unemployment has reached a 45-year high, he said.
"That's why jobs are declining, recruitment processes have collapsed, and the future of youth is being jeopardised. That's why every exam paper leak and every recruitment is linked to stories of corruption," Gandhi said.
भारत में युवाओं की सबसे बड़ी समस्या बेरोज़गारी है - और इसका सीधा रिश्ता वोट चोरी से है।
— Rahul Gandhi (@RahulGandhi) September 23, 2025
जब कोई सरकार जनता का विश्वास जीतकर सत्ता में आती है, तो उसका पहला कर्तव्य होता है युवाओं को रोज़गार और अवसर देना।
लेकिन BJP चुनाव ईमानदारी से नहीं जीतती - वो वोट चोरी और संस्थाओं को कैद कर… pic.twitter.com/DlDmdYOl5i
"The country's youth work hard, dream, and fight for their future. But (Prime Minister Narendra) Modi is solely focused on his PR, getting celebrities to sing praises for him, and billionaire profits. It has become the government's identity to shatter the hopes of the youth and leave them frustrated," the former Congress chief said.
"Now, the situation is changing. India's youth understand that the real fight isn't just for jobs, but against vote theft. Because as long as elections are stolen, unemployment and corruption will continue to rise," he said.
Young people will no longer tolerate "job theft" or "vote theft", Gandhi asserted.
"The ultimate patriotism now lies in freeing India from unemployment and vote theft," he said.
Gandhi also shared a split screen video montage of police lathi-charging protesting students seeking jobs on one half of the screen and Prime Minister Modi planting saplings, feeding peacocks and practising Yoga on the other half of the screen.
