Airborne transmission is a major risk for the spread of viruses in enclosed spaces . Therefore, air ventilation with quality extractors and ducts is essential to reduce this risk. This is something that has been reinforced by the Covid-19 pandemic , since after practically two years we know that the virus that causes the disease spreads mainly through aerosols.
A team of researchers from the Indian Institute of Technology in Mumbai (India) has carried out computer simulations of the flow of air inside a public toilet to demonstrate how infectious aerosols can remain up to 10 times longer in certain dead zones of a room. .
Where are these dead zones?
“The virus travels inside tiny microscopic droplets or aerosols that come out of the mouth when we speak, shout, sing, cough or sneeze. Then it floats in the air, where it can be inhaled and transmitted,” the statement issued by the researchers details.
The research, which has been published in the journal ‘Physics of Fluids’ , has revealed that these dead zones are most often located in the corners of a room or around furniture.
“We explored a small, one-person facility used by many, one after another,” says Krishnendu Sinha, professor of aerospace engineering at the Indian Institute of Technology in Bombay and one of the study’s authors. “I have a similar bathroom in my house, which facilitated their study. Mobility was restricted and the laboratories were closed, but this allowed us to continue our study during the confinement.”
How should the ventilation be in closed spaces?
The researchers found that the chances of transmission and infection are much higher in these dead zones that ” can be near a door or window, or right next to an air conditioner that is blowing air,” adds the expert.
The simulations show “air flows in tortuous routes, like a vortex,” explains researcher Vivek Kumar, co-author of the study. “Air has to be continuously removed from every part of the room and replaced with fresh air. This is not easy to do when the air is recirculating in a dead zone.”
So how should these spaces be ventilated? “Currently, ventilation design is often based on air changes per hour (ACH),” argues Professor Sinha. “These design calculations assume that fresh air reaches all corners of the room evenly. From computer simulations and experiments inside a real bathroom, we know this does not happen.”
For this reason, he explains, for ventilation to be effective against viruses it is necessary to “place ducts and fans based on air circulation within a room,” he concludes.