This was discovered by a US research team evaluating the effects of different ventilation strategies and spacing on the transport of aerosols: “Particles can move quickly from another person’s breathing zone in one minute, even covering a distance of two meters. “.
An interpersonal distance of 2 meters may not be sufficient to reduce the risk of exposure to viral aerosols indoors. This is what emerges from a new study published by a research team at Penn State University in the scientific journal Sustainable Cities and Society which evaluated the effects of different building ventilation strategies and interpersonal distancing on the transport of indoor aerosols.
The analysis examined three factors: the quantity and speed of the air in the rooms, the displacement of the air flows associated with different ventilation strategies and how respiratory aerosols are emitted, tracking how particles can move from one person’s breathing zone to another. “Our results reveal that virus-laden particles emitted by an infected person speaking without a mask can travel rapidly, covering a distance of two meters within one minute”Explain the authors of the study.
This trend, particularly evident in poorly ventilated environments, has also been confirmed in environments with displacement ventilation, that is, where the fresh and clean area is introduced at floor level, pushing old and potentially contaminated air towards the vents arranged at the level of the ceiling.
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This type of ventilation, the researchers point out, can lead to a concentration of viral aerosols in the human breathing zone up to seven times higher compared to ventilation systems a mixed mode, which instead provide for the introduction of external air in order to uniformly dilute the internal one, so as to maintain a better mixing of the tempered air and at the same time a lower concentration of aerosols.
A divergence, the latter, which the researchers did not expect to observe, and which can be further expanded increasing ventilation and air mixing speed. “These two options can effectively reduce transmission distance and the potential build-up of exhaled aerosols, but they are only two alternatives in an arsenal of protection strategies. – noted Donghyun Rim, the study’s corresponding author and associate professor of architectural engineering at Penn State University. Measures to prevent airborne infections, such as physical spacing, ventilation and the use of the mask they should be considered as a whole, for multi-level control”.
The results achieved by the researchers therefore confirm that masks remain very important in limiting the risk of viral transmission, although ventilation strategies greatly affect the airborne transmission of aerosols. Therefore, the scholars’ work has now focused on analyzing the transport dynamics of exhaled aerosols in other contexts, such as in classrooms and on public transport, including buses and trains.