Two studies on how fluids propagate in the air reveal new information on the transmission of covid in enclosed spaces, one of the main issues in the current phase of coexistence with the SARS-CoV-2 coronavirus. The first work sheds light on the cloud of droplets released when we cough and on the effectiveness of the masks in containing it; the second analyzes the effects of ventilation in the rooms and explains why it is advisable to air the rooms we live in often.
How far does covid spread by air?
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Put on the mask. The first research, published on Physics of Fluids by two scientists at the Indian Institute of Technology Bombay, proposes a model of how the volume of the cloud of particles exhaled with cough changes with the passage of time. The researchers found that the first 5-8 seconds after coughing are those in which the emitted droplets remain suspended in the air, and are therefore crucial for the spread of any infection. After that period of time, the cloud of droplets begins to disperse. However, the most interesting data concerns the masks: wearing a surgical one reduces the volume of the cloud of infectious particles emitted by coughing by 7 times, while the N95 model, more filtering, thins it by as much as 23 times.
“Anything that reduces the distance covered by the cloud, such as a mask, a handkerchief or coughing in the crook of the elbow, should also greatly thin the region over which the droplets disperse and therefore the chances of infection” explains Rajneesh Bhardwaj, among the authors.
The mask also protects the wearer
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Open the windows! The second study, published in the same scientific journal, he instead explored the journey of infected aerosols in a closed, air-conditioned room, such as a classroom or an office. From the model, developed by scientists from the University of New Mexico, it can be seen that a simple gesture like opening the windows increases the share of particles exiting the system by more than 40%.
According to the authors, the flow of air inside a closed room means that between the people present there is still a significant exchange of particles (equal to 1% of the total emitted) even when a distance of 2.4 meters. However, when the windows are opened, almost 70% of the particles of one micrometer (one thousandth of a millimeter) are released.
The importance of well-ventilated rooms. According to the model, the air conditioning can remove up to 50% of the particles emitted by breathing or speaking, but the remaining amount settles on the surfaces inside the room, and from there it could be put back into circulation (it is therefore essential hand hygiene). The research also confirmed that the distribution of residual aerosols is not uniform but varies according to the points of the room and that the plexiglass barriers protecting the desk or counter obstruct the passage of local air, close to the subject, diverting the trajectory. particles and making contagion less likely.
Late US admissions on airborne virus transmission
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fundamental precautions. Research such as these provide important information on how to limit infections in closed and crowded places, where you have to attend them in person. Always wear masks, keep windows open, improve ventilation systems, install transparent barriers around tables and place those most at risk in the points least exposed to the passage of particles (which vary depending on where the systems have been placed. conditioning) are measures that reduce the risk of contagion.
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