If the respirator does not seal well, its effectiveness decreases and it protects less from the spread of infection. Face shields capture only large droplets, but not the aerosol. Why is it important to ventilate? Can air purifiers help? Questions related to the aerosol effects on the spread of coronavirus are answered in detail in a document by German experts. Their colleagues from the Brno University of Technology, the Institute of Chemical Processes of the Academy of Sciences of the Czech Republic and the Czech Metrology Institute under the auspices of the Czech Aerosol Society translated it and offered it to the public.

Aerosol transmission of SARS-CoV-2 is considered to be one of the most important modes of its spread, along with touch and droplet infection. Aerosols are tiny particles dispersed in the air. Man creates them not only when coughing or sneezing, but also when breathing itself. Some such particles may carry a virus. "There is a wealth of information circulating among professionals and the general public about coronavirus and its spread. However, this information may not always be correct or understood correctly. Given that we have been studying aerosols and their behaviour for a long time, we, as members of the Czech Aerosol Society, considered it our duty to bring a little more light into this issue,” Jakub Ondráček explains, the Secretary of the Czech Aerosol Society (ČAS). "German colleagues recently published a relatively comprehensive document, which we consider to be very relevant, and we dared to translate it into the Czech language. This summary text should serve both the lay and professional public to better understand the spread of the virus in the form of aerosol particles and also as a meaningful basis for measures to prevent the spread of the virus," Ondráček, who studies the issue at the Institute of Chemical Processes, adds.

Thanks to good relations with the German Society for Aerosol Research (Gesellschaft für Aerosolforschung, GAeF), Czech scientists have obtained permission to translate the original text. The document is published on the website of the Czech Aerosol Society.

"This is a professional text, the purpose of which is to provide the verified information needed for the right decisions against the spread of a pandemic. It is primarily intended for everyone who makes such decisions, but we will be happy if they are of interest to the general public. For example, it explains to physicians and medical societies how the virus spreads physically. These mechanisms are important for understanding which measures make sense and which do not. For the average reader, the chapter on the effectiveness of personal respiratory protective equipment may be interesting," the initiator of the translation František Lízal from the Faculty of Mechanical Engineering, Brno University of Technology, says.

One measure will not stop the virus

Right at the beginning, German experts summarize current knowledge about the measures to manage the pandemic. And they point out that none of them can work independently. According to them, the best way to reduce the risk of infection is to combine several different types of measures at the same time. Spacing is important, respiratory protection is crucial, but it is important to know the limits: for example, respirators with an exhalation valve serve only to protect the wearer, not the surroundings, and the use of non-respirator face shields is essentially ineffective against the aerosol spread. In the outdoor environment, the spread of infection through aerosols practically does not occur if people do not accumulate, on the contrary, in indoor spaces, the risk is greater.

Lízal hopes that the text will help readers to better understand how the particles behave and, on that basis, to choose the right protective equipment. "It's important to understand that if I have the best respirator, but it doesn't seal well, it will definitely not give me enough protection. In addition to respirators, we must not forget about ventilation or use air purifiers," Lízal points out.

Experts' knowledge of the virus and its behaviour is constantly being refined. "I myself have learned a lot in the last year and I have had to study a lot. A huge number of scientists have embarked on research into this issue, whose professional articles are no longer in the power of one person to absorb all of them. That is why we wanted to translate the summary of knowledge from our German colleagues into Czech,” Lízal adds.

At the end of the text, aerosol experts set out for themselves and their scientific colleagues other research tasks that should help them better understand the spread of the virus and thus fight the pandemic.

You can find the whole document on the website cas.icpf.cas.cz