Given the current pandemic situation at Covid-19, Manuel Gameiro da Silva, professor at the Department of Mechanical Engineering at the Faculty of Science and Technology of the University of Coimbra (FCTUC), warns that indoor air quality is critical.
Therefore, says the air conditioning specialist, as long as the pandemic crisis persists, "in-person meetings should not be held and indoor spaces with human occupation should be strongly ventilated, exclusively with fresh air, to reduce virus concentrations, in the case of contamination by airborne particles, and thus reduce the risk of infection'.
Manuel Gameiro da Silva also argues that “when planning a trip to places frequented by other people, you should wear a mask and, if possible, a visor. Normal masks are not completely effective in retaining the smallest particles, so the use in combination with a visor substantially increases the retention efficiency».
These alerts are the result of an analysis that the UC scientist decided to carry out due to the doubts raised about "the importance that health authorities, both nationally and internationally, attribute to the role that different modes of transmission play in the spread of viral infections and the consequences that may result from them'.
The author considers that, "without there being scientific evidence to justify it, the role that can be played by transmission through the mode of suspended particles has been diminished and that, as a result, some of the protective measures that, they will likely be at the base of the more modest rates of spread of the epidemic in some Asian countries».
There is no doubt that the new coronavirus, SARS-Cov-2, is transmitted mainly through particles exhaled by contaminated patients, Manuel Gameiro da Silva explains that the different modes of transmission of infectious diseases are associated with particles of different sizes: particles large (greater than 50 microns), which are exhaled and deposited on surfaces, are responsible for transmission by contact; the intermediate particles (from 10 to 50 microns) are responsible for the direct transmission from the emitter to the receiver, called droplet transmission; finally, the smallest particles (less than 10 microns) are responsible for the mode of transmission by suspended particles, which can remain in the air for hours, be transported over long distances and inhaled.
Regarding the effect of temperature and humidity, the coordinator of the UC's Energy for Sustainability Initiative says that «typically, the persistence of viruses is higher at cold temperatures than at hot temperatures, and as humidity destabilizes the protective layer of fat from Coronavirus-type virus, virus persistence is greater in dry environments. Solar radiation has an ultraviolet radiation component that impairs the persistence of viruses so that, in indoor environments without direct natural light, there are more favorable conditions for the persistence of viruses as particles in suspension».
Manuel Gameiro da Silva defends the «redefinition of the concept of safety distance between people and the need for generalized use of protective equipment for the upper airways (masks and visors) whenever it is anticipated that one will be in an environment with multiple occupation».
Note: This analysis is part of the UC Against Covid-19 platform that has just been launched by the University of Coimbra.
Author: Cristina Pinto, University of Coimbra – Science Communication
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