Scientists at Charité – Universitätsmedizin Berlin and TU Berlin have developed a new method that enables the quantitative measurement of aerosol quantities transmitted between people in any specific environment In the future, this method could be used to better assess the probability of SARS-CoV-2 aerosol transmission in specific situations.
The measuring technique allows the scientists to compare different rooms, environments, and situations, as well as preventative measures.
By far the most likely way to transmit SARS-CoV-2 is an infection resulting from droplets and aerosols in room air. Aerosols are a group of minuscule droplets or solids, such as dust particles or viruses – thus scarcely visible to the naked eye. This make it all the more difficult for people, particularly decision makers, to assess the actual infection potential in any given situation.
Scientists from the Institute of Fluid Dynamics and Technical Acoustics at TU Berlin and the Chair of Fluid Dynamics, headed by Professor Oliver Pashereit, have worked together with a team under the direction of Dr.-Ing. Ulrich Kerzscher, head of the Biofluid Mechanics Lab at Charité, to develop a measurement method allowing the quantitative measurement of aerosols transmitted from one person to another in any specific environment and situation.
To achieve this, they use human-like dummies. One is the so-called emitter, that is a person who emits aerosols that are comparable to the human cough in terms of droplet size distribution. Other dummies, the so-called absorbers who breathe in the surrounding air, are located at specific positions around the room. The aerosol droplets emitted contain a substance that serves as a substitute for potential viruses. Their concentration is then measured quantitatively in the inhaled air of the absorbers. This ‘tracer’ behaves like viruses. While the liquid in the aerosols has already largely evaporated, it continues to move around freely through indoor air.
“This enables us to accurately determine the amount of aerosols a single absorber takes in from different positions in a specific room,” explains Oliver Paschereit. Using the new method, the researchers can concretely determine the risk of aerosol transmission in different everyday situations and evaluate them against each other. The pilot project was conducted at the Berlin Philharmonie. However, this new technique may also make it possible to identify and assess the risks in public transportation, restaurants, meetings, or at gatherings outdoors.
“Our measuring technique can show in concrete terms whether viruses collect in room air in a particular setting, such as a concert hall, or whether they can be removed through efficient room ventilation or airing. Even though, of course, we cannot model actual infection incidents with our method, the measurement results at least provide us with an estimate of the likelihood of viral transmission from one infected person to a number of other people,” says Ulrich Kertzscher. The scientists believe there are many possible uses for their technique and have already filed a patent application.
“Such measurements could be of particular interest, for instance, to event organizers, to quantify the aerosol spread in their venues,” emphasizes Dr. Sebastian Schimek, another researcher in Paschereit’s team. Additionally, decision makers who have to deal with super-spreader events and visitors to public events may be interested in an improved assessment of the aerosol spread. “Of course, no direct risk of infection for individuals can be deduced just from the number of aerosols transferred. However, it does allow us to compare the risk associated with different situations where people come into contact with each other,” explains Vera Froese, a member of the Biofluid Mechanics Lab.