Maintaining indoor humidity can limit airborne transmission of coronavirus

Keeping indoor humidity levels between 40% and 60% will help limit airborne transmission of the novel coronavirus by minimizing the presence of infectious viral droplets in the air, according to a new study.

The authors said that as the amount of water vapor in the air rises, viral droplet size increases and the heavier droplets fall from the air more quickly, providing less chance for other people to inhale them and become infected.

By contrast, when humidity is low, the virus-containing droplets dry out – but the small infectious virus particles survive, floating in the air for longer periods and flying further through the room, depending on ventilation conditions, the researchers said in the journal Aerosol and Air Quality Research.

Dry air also dries out the mucous membranes in the nose and makes them more permeable to viruses. Authorities should include humidity factors in future indoor guidelines, study co-author Dr. Sumit Kumar Mishra of CSIR – National Physical Laboratory in New Delhi said in a press statement.

The findings are relevant not just in cold winter climates, his team said. Countries in tropical and hot climates should take care that indoor rooms are not dried out by overcooling with air conditioning.