Further research points to a growing body of evidence that indoorventilation may be a key contributor in prevention of COVID-19. However, theventilation must be effective.
The study, published in the journal EnvironmentInternational, found that SARS-CoV-2 is rather moderately infectious and aperson would need to remain in a poorly ventilated room for a considerableamount of time to receive an infectious dose of SARS-CoV-2.
"Multiple studies provided quickly strong scientificevidence for successful indoor airborne transmission of Covid-19 ininadequately ventilated environments," said study author Jarek Kurnitskifrom Estonian Research Council in Estonia.
"The virus is transmitted via saliva droplets with asize from 0.5 micrometres up to a few thousand micrometres produced by a personby talking, sneezing, coughing, or even just breathing," Kurnitski added.
According to the researchers, the point is that small andlarge droplets act completely differently. Tiny droplets below 5 micrometres donot settle on surfaces, they remain airborne and follow airflow streamlines fortens of metres.
Large droplets above 100 micrometres in diameter fall downlike rocks - they do not travel farther than 1.5 metres even by coughing.
The air exhaled by humans contains mainly droplets with adiameter in the range of 1-10 micrometres.
Until this spring, it was held in the medical literature andguidelines that droplets larger than 5 micrometres fall down at the distance ofup to two metres (which is why it was concluded that 2-metre social distancingwould ensure complete safety).
By now, however, scientists have found out that this was amisconception or even a long-persisting erroneous medical dogma.
Aerosol physics shows convincingly that in reality onlydroplets larger than 50 micrometres fall down at a distance of two metres,while smaller ones remain suspended in the air and travel farther.
Thus, acknowledging this tenfold error fundamentally changedthe understanding of the spread of virus particles and it was realised that thelargest number of exhaled droplets travel far and the virus can remaininfectious in aerosol particles for up to three hours.
By breaking this medical dogma, researchers also gave animportant signal regarding the measures applied to prevent the spread ofCovid-19 that led to the paralysis.
"Measures can and must be applied taking into accountthe known transmission routes, which is why it is important to know that thedisease is transmitted by aerosols, i.e. tiny droplets suspended in theair," the authors wrote.
This means that people can get the virus in two ways: inclose contact, where the concentration of aerosols and larger droplets in closeproximity of the infected person is very high.
Kurnitski noted, "Or farther away in inadequatelyventilated rooms, where the concentration of aerosols remains so high that aperson can get an infectious dose for example within an hour spent in the sameroom with an infected person."