More than a year after the declaration of the coronavirus pandemic, aerosols remain the main reason for contagion. For this reason, the importance of good ventilation in closed spaces is highlighted, as well as the meeting of groups in outdoor areas. And it is that, a publication made by the Chan School of Public Health of Harvard University, Boston, the Taubman College of Architecture & Urban Planning of the University of Michigan and HOK Architects, Chicago, in Jama Network, highlights that the smallest aerosols can stay in the air from 30 minutes to hours. They can even travel up to two meters indoors.
As explained in the study, the largest aerosol droplets – considered greater than or equal to 100μm (micrometer) – can remain in the air thanks to their gravitational forces, as well as moving up to two meters in interior areas without ventilation. However, they point out that people emit aerosols a hundred times smaller than that length – less than 5μm. Talking, coughing and even breathing is enough to project these aerosols, that would remain suspended in the air for at least 30 minutes, although they can take hours to spend in the same space.
“Lack of engineering” in the interiors
Therefore, the publication highlights that COVID-19 infections in restaurants, gyms, practices in groups, schools and buses are related to the characteristics of closed environments. What does it mean? Well, areas with little ventilation in which we spend a long period of time, even if the social distancing measures are met.
Given the number of infections, the experts detail in the publication that there is a “lack of engineering” in the interior spaces, which do not have beneficial ventilation to avoid a spread of coronavirus through aerosols. And is that these buildings, unlike hospitals, are not designed for infection control.
Ventilation, a key factor against COVID
And what should we do to reduce aerosols? The study emerges that, in confined indoor spaces, “4-6 air changes per hour are applied, through any combination of: outside air ventilation; recirculated air passing through a filter with at least a minimum efficiency rating of 13 (MERV 13); or the passage of air through portable air purifiers with HEPA filters (high efficiency particulate air) ”.
“Increasing hourly air changes and air filtration is a simplified but important concept. that could be implemented to help reduce the risk of airborne transmission of SARS-CoV-2 and other infectious respiratory diseases inside the room and from the air. Healthy building controls, such as increased ventilation and better filtration, are a critical, but often overlooked, part of risk reduction strategies that could have benefits beyond the current pandemic ”, the authors add as a conclusion to the study.
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