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Transmission via aerosol
More and more studies confirm that the transmission of the new coronavirus occurs through tiny droplets (aerosols) that infected people exhale not only when coughing or sneezing (in addition to droplets that, heavier due to their larger size, fall to the ground during force of gravity following ballistic trajectories within two meters) but especially when they speak, sing, shout, breathe. Furthermore, recent studies suggest that aerosols can move several meters in the room and remain for long periods maintaining an infectivity load. And now that we are approaching the winter season, the risks increase (as with the flu and other respiratory viruses) because more time is spent indoors and the concentration of infectious particles increases without adequate ventilation. The critical places are closed rooms of small size and limited ventilation, especially with a long residence time. Giorgio buonanno, Senior Lecturer in Environmental Technical Physics at the University of Cassino and Queensland University of Technology in Brisbane (Australia) who studied how to estimate the risk of contagion in closed environments, suggesting interventions to keep contagion rates acceptable (SEE HERE).
Mobile air purifiers in schools
The aim of the German government is above all to improve existing ventilation systems instead of installing new ones, which are more expensive. Even schools, without ventilation systems, will at least be equipped with mobile air purifiers to increase ventilation and reduce the risk of contagion (the cost is around two thousand euros).
The importance of ventilation in Germany
In Germany, room ventilation is one of the official measures to prevent Covid. The custom of opening windows even in the middle of winter is something of a national obsession for Germans, even before the arrival of Sars-CoV-2, so much so that it is often a requirement inserted as a legally binding clause in rental contracts ( more than anything else). to protect environments from mold and odors). It can be one of the cheapest and most effective ways to contain the spread of the virus, as you have repeatedly pointed out. Angela Merkel. The German government’s guidelines for dealing with the virus, encapsulated in the acronym AHA, which stands for distancing, hygiene and facial coverage, have been expanded to become AHACL. The “C” stands for the government’s coronavirus warning app and the “L” for Lften or air a room. Regular impact ventilation in all public and private facilities can greatly reduce the risk of infection, explains the government recommendation. Impact ventilation, or Stosslften, involves opening a window in the morning and at night for at least five minutes to allow air to circulate. Querlften, or cross ventilation, is even more efficient, in which all the windows in a house or apartment are opened, letting out stale air and letting in fresh air. Even schools have long embraced this practice, to which meetings between public health administrators and newspaper pages are devoted. Recently, five experts – from fluid mechanics to aerodynamics and indoor air hygienists – reiterated the importance of ventilating a classroom every 15-20 minutes, for five minutes in spring and fall and three minutes in winter. Keeping windows wide open to clear the air in the dead of winter cools the temperature dramatically at the risk of having to take lessons in coats … hence the option to invest in forced ventilation.
What is not enough?
But spacing and mask not enough to protect you indoors? The correct use of surgical masks reduces the chances of infection by aerosols, although not decisively. This is because surgical masks are not specifically created for typical aerosol size particles, explains Giorgio Buonanno, who adds: Face filters (FFP2, FFP3, N95) are certainly more efficient, as they have very filtration efficiency. high, even for typical aerosol size. The spacing – concludes the expert – avoids coming into contact with the droplets and high concentrations of aerosols in the vicinity of the infected subject but would still be transmission via aerosol at greater distances in closed environments because the particles move to greater distances before evaporating to two meters. This mode of contagion is not considered by the measures adopted. Is that why in Italy, despite the obligation of masks and spacing, the contagion curve is rising so steeply?
October 20, 2020 (change October 20, 2020 | 4:33 PM)
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