France: the reopening of the rooms and the question of the transmission of the Covid in the air
Artists and professionals from the world of culture during the occupation of the Théâtre de l'Odéon, in Paris, on March 12, 2021. REUTERS - Benoit Tessier
Text by: Alexis Bedu Follow
6 mins
In two weeks, on May 19, shops, theaters and cinemas will be able to reopen in France.
How is Covid-19 transmitted through the air in these closed places?
And what are the risks?
These are crucial questions for the success of the future deconfinement according to scientists.
Because the transmission of the virus in the air is now recognized by all.
There is no shortage of examples of contamination around the world.
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Recently, an epidemiological investigation carried out in Australia and reported in a scientific journal, gave valuable indications in the transmission of the virus in the air. In July 2020, a chorister from a parish in Sydney tested positive for Covid-19. During his phase of contagiousness, he sang at four masses of one hour each. A few days later, two other choristers and twelve faithful, attending the services, will test positive. Some of them were however seated about fifteen meters from the infected chorister. The ventilation system installed in the church was not working that day. The doors and windows were closed. To limit the spread of the virus, the droplets emitted by this chorister would have had to be found in small numbers in the air.
"If everyone wears masks, we are safe"
Today, the main challenge is to estimate the level of presence of these aerosols when we are in an enclosed space.
Because it is the first vector of contamination, far ahead of infected surfaces which only represent a minimal number of infections.
Some physicists have recently focused on calculating the level of CO2 in a room. This is the case of teacher-researcher Florence Elias. Thanks to a sensor installed in a classroom with her students, she measured the level of carbon dioxide. Interesting to know if a room is sufficiently ventilated. “
When we measure a CO2 concentration beyond the initial concentration, we know roughly the proportion of air that has been breathed by someone in the room,
confides Florence Elias.
If we have a CO2 detector, we can try not to exceed this threshold which is currently set at 800 parties per million, that is to say 0.8% of CO2 in the room.
If it is well ventilated, if the air is sufficiently renewed, so if someone is contaminated in the room, the amount of virus in the room will not be very large.
So, we believe that if everyone wears masks, we are safe. ”
The Projet CO2 association, of
which Florence Elias is a member, therefore recommends the installation of CO2 detectors everywhere in France.
The main studies carried out, particularly in Germany and the United States, show more or less the same thing: halving the excess CO2 compared to an outdoor space halves the risk of contagion.
New video !
HOW TO LIMIT THE AIR TRANSMISSION OF COVID?
🦠➡️🪟
I present to you some calculations resulting from a recent article, making it possible to establish and limit the risks of exposure, in particular in the classroom. Https://t.co/UpudrOJuPm pic.twitter.com/1R7E0ZtC2X
- David Louapre (@dlouapre) April 30, 2021
Aeration is a very important barrier gesture
Another scenario on which, studies insist, removing your mask when you are alone will not prevent contamination.
Doctors and scientists recall it two weeks before the reopening of so-called non-essential businesses in France.
Putting back his mask only when a customer enters the store does not prevent the transmission of the virus.
Potentially infectious aerosols are still in the room if the air has not been renewed.
"
The number of people in an elevator at the same time is limited. But if you got out of the elevator and someone comes in, the person is going to breathe in the viruses that were just released in the elevator. Aeration is a very important barrier gesture to be able to open closed spaces such as the theater, performance halls, classrooms, etc.
», Recalls Florence Elias.
Curious experiment carried out by American researchers.
They put the flies in contact with Sars Cov2 infested milk for 24 hours.
Result: all the insects were carriers of the infectious virus.
These same infected flies were then placed in another container.
Clean that one.
After 24 hours, it was shown that they had deposited viral RNA on the walls of the container.
Flies carry the virus.
But they contaminate very, very little.
Today there is no danger of transmission to humans.
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