What we know about aerosols and COVID-19

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The Society for Aerosol Research has summarized the current state of knowledge and formulated a recommendation for protection against coronaviruses. Bernadett Weinzierl, head of aerosol physics and environmental physics at the University of Vienna, was also involved as the main author.

Aerosols have probably only become known to the general public through reports on the COVID-19 pandemic. The fact that coronaviruses can spread via aerosol particles and thus lead to infections has now been confirmed by many scientific studies. Now the Society for Aerosol Research e. V. (GAeF) together with more than 185 international experts summarized the current state of knowledge on the subject of aerosols in an easily understandable way and formulated recommendations for protection against the virus.

One of the main authors of the position paper is Bernadett Weinzierl, Head of Aerosol Physics and Environmental Physics at the University of Vienna and former Deputy President of the GAeF. “The aim is to explain the currently frequently used term ‘aerosol’, to clearly illustrate the most important aerosol processes and thus to make a contribution to overcoming the pandemic,” said Weinzierl.

What is an aerosol?

An aerosol is a mixture of air with solid or liquid particles. Since the particles are usually very small and constantly changing, measuring and controlling them is difficult.

Corona virus: how it changes our lives
From new family processes to the effects on logistics chains: Experts from the University of Vienna talk about the consequences of the corona virus in a wide variety of areas. (© iXismus / Pixabay)

What we know about aerosols and what works against COVID-19

The most important findings of the GAeF experts can be summarized in these points:

No measure can work on its own. According to the current state of knowledge, the interaction of the various measures is the best way to minimize the risk of infection.

Keeping your distance is important. With increasing distance, viruses directly exhaled are diluted and the likelihood of being infected decreases. In addition, large drops are given the opportunity to sink to the bottom. The often prescribed minimum distance can serve as a guide, but should be increased and supplemented by further measures, especially for longer gatherings and also indoors with reduced air movement.

Masks help filter some of the exhaled particles (and viruses). This reduces the concentration of the emitted particles in a room and thus the risk of infection. It should be noted that the exhaled aerosol particles are relatively large due to adhering moisture and can therefore be efficiently retained by simple masks. However, since these particles shrink the longer they remain in the room air, simple mouth and nose covers are less efficient for self-protection. This requires breathing masks that have a high filter effect even for fine particles, e.g. B. of the classes FFP2, N95 or KN95. These are efficient for both self and external protection, provided they do not have an exhalation valve. Masks with an exhalation valve, on the other hand, only serve for self-protection and therefore contradict the solidarity concept that fellow human beings are protected by collective mask wear.

The Society for Aerosol Research e. V. (GAeF) was founded in 1972 as a non-profit association of pioneers in aerosol research in German-speaking countries (Germany, Austria, Switzerland) and beyond and has set itself the task of promoting scientific aerosol research nationally and internationally.

Do visors and air purifiers help?

Face visors are largely useless in terms of aerosol particlesif they are used without the additional use of masks, as the air with particles (and viruses) flows unfiltered around the visors. Face visors are worn in addition to masks in everyday clinical practice in order to prevent droplet infection via the mucous membranes of the eyes. Mobile or permanently installed plexiglass barriers are also largely ineffective against the spread of aerosol indoors. These can only temporarily prevent the small-scale spread of an aerosol, e.g. B. in the checkout area of ​​a supermarket. Face visors and plexiglass panes essentially serve as spit and splash protection against large droplets.

In the open air there are almost no infections via the aerosol. In closed spaces, ventilation is essential to replace the exhaled air in a room with fresh air from outside. Intermittent and cross ventilation are as effective as leaving the window completely open all the time. From an energetic point of view, however, intermittent or cross ventilation is more efficient, especially in winter. CO2 monitors can help monitor indoor air quality. However, they can only be used as an indicator and do not prevent direct infection even if the suggested CO2 limit concentrations are observed.

Air purifiers can make a meaningful contributionto reduce the concentration of particles and viruses in a room. When purchasing air purifiers, care must be taken to ensure that they are sufficiently dimensioned for the intended space in order to actually significantly reduce the particle and virus load. The air throughput of the device is more important here than the efficiency of the filter. Permanently installed ventilation systems can also be useful, provided they filter the air in order to reduce the particle and viral load in a room. To avoid infections, it makes sense to operate them with a 100% fresh air supply if possible.

The complete paper including images can be downloaded for free from the GAeF website https://www.info.gaef.de/positionspapier

Bernadett Weinzierl is Professor of Aerosol and Cluster Physics at the Faculty of Physics at the University of Vienna. Her focus is on aerosol physics, aerosol-climate interactions as well as ground-based and airborne in-situ measurements. (© Barbara Mair)



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https://medienportal.univie.ac.at/uniview/forschung/detailansicht/artikel/aerosole-und-covid-19-was-wissen-wir/

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