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A conversation without a mask - in Corona times that can mean a danger
Photo: Klaus Vedfelt / Getty Images
Aerosols play a crucial role in the spread of the Sars-CoV-2 pathogen.
They arise when breathing, coughing, sneezing - but also when talking or singing.
And they carry the virus piggyback, so to speak, and thus help it spread.
Larger droplets don't make it very far, that's the reason for distance rules.
But smaller particles can stay in the air for hours if not ventilated.
This is problematic indoors.
There are now a few computers on the Internet that interested parties can use to estimate the corona risk in such situations.
One of them comes from the Max Planck Institute for Chemistry in Mainz and the Cyprus Institute.
A team led by fluid mechanic Pedro Magalhães de Oliveira from Cambridge University in the UK has now presented a new computer in the journal Proceedings of the Royal Society A.
The research provides an interesting finding: speaking to an infected person could be just as problematic because of the aerosols that are emitted as when this person coughs into the air.
Specifically, the researchers simulated that 30 seconds of speech produce significantly more aerosols under five micrometers than a brief cough.
This means that more infectious material reaches people in the area - enough, according to the simulation, to actually trigger a corona infection.
The team concludes from this that distance alone in the absence of ventilation is not sufficient to provide safety during long exposure times.
Instead, the well-known combination of measures is necessary: "You need masks, you need a distance, and you need good ventilation so that these particles do not collect in an interior space and they are safely removed," says de Oliveira in the Guardian.
"Very important point that must be taken into account"
Speaking is a "very important point that has to be taken into account" because it produces much finer particles than when coughing, says de Oliveira.
Whether there is actually an infection depends on many factors, several of which can be set in the computer: How large is the area of the room in question?
How high is this?
How often is the air exchanged?
How many people are there for how long?
What masks are they wearing?
An example: A shop with an area of 250 square meters is open from 7 a.m. to 8 p.m., and a maximum of 50 customers can shop at the same time.
They all washed their hands, obeyed the rules of distance and are wearing a simple cloth mask.
If, from a statistical point of view, there is always one sick person in the shop, the risk of infection depends heavily on the ventilation:
If the air is
renewed
once an hour
, as the researchers estimate for living spaces, a person would have an estimated probability of
about 2.7 percent of
contracting the coronavirus
after two hours
.
Assuming an air exchange rate of
three times an hour
, as is assumed for offices and schools, the risk drops to
around 1.6 percent
.
With good ventilation (air is
exchanged
five times an hour
) to
around 1.1 percent
.
The computer can also be used to simulate the effect of wearing surgical masks or FFP2 masks instead of simple cloth masks, as is now mandatory in Germany in supermarkets and public transport.
Of course, it is important that such calculations are always based on certain assumptions, in the specific case for example a comparatively high viral load.
The new corona mutants are also not yet taken into account.
These are considered to be significantly more infectious than the previous virus variants.
In principle, computers like the one from de Oliveira and his colleagues can help to estimate the effect of certain measures.
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