The Istituto Superiore di Sanit has updated the recommendations on sanitation for non-health facilities in the current Covid-19 emergency, meaning by sanitation an activity relating to both surfaces, both environments. For the first time airborne transmission of the coronavirus is given priority. The highest concentrations of viral load are present in the vicinity of an infected subject, however infections from Sars-CoV-2 can also occur at greater distances through theinhalation of airborne virus-laden particles in indoor spaces not properly ventilated, shared with infected individuals. Airborne transmission is known to be the dominant mode of many respiratory infections, particularly in poorly ventilated environments, write the experts who drafted the recommendations. On the basis of the knowledge acquired over the months, international organizations recognize airborne transmission as a significant mode of contagion rather than through contact with surfaces. Consequently, more attention is now required on aspects concerning the sanitization of the air and environments rather than on surfaces: contact with contaminated surfaces in fact now considered a mode of transmission of the virus extremely rare (the American CDCs speak of 1 in 10 thousand).
Surfaces and air
The guidelines reiterate the already known methods for disinfecting the various surfaces with virucidal products based on sodium hypochlorite or alcohol, but great attention is paid to frequent air exchange at least with the opening of the windows (the complete exchange can be monitored with the use of CO2 sensors) or in any case with portable air purifiers where it is not possible to intervene with mechanical ventilation systems.
The different scenarios
Unfortunately, there is no magic number of air changes necessary to prevent Sars-CoV-2 contagion because several factors come into play: quality of the air used for the exchange, number of people present, type of activity carried out (more aerosol when talking loudly or doing sports), size of the rooms, type of ventilation. The scenarios are different and must be assessed on a case by case basis. However, there are models that allow you to provide the right information. It is clear that a principal or a restaurateur who find themselves having to decide how to mitigate the risk of contagion, as regards ventilation, should rely on specialized bodies to find the right solution.
Ventilation alone is not enough: the other parameters
In the document it is confirmed that ventilation alone is not sufficient to reduce the risk to acceptable values. it is necessary to take priority action on emission reduction. For Sars-CoV-2 it has been seen that passing from simple breathing to speaking aloud or singing, the increase in aerosol particles emitted increases up to 100 times. For this reason in schools it is suggested to teachers, who must keep a high tone of voice to explain, to usemicrophones so you can lower your voice and emit less aerosols. In this way, in a standard class, three complete air changes would be enough to have an Rt lower than 0.75. In restaurants, however, where it is not possible to reduce the emission of the source (since people converse aloud without other protections), it is suggested to intervene, next to the ventilation, on the residence times e crowding. Again there are models applicable to reduce the risk.
The technologies available
The document lists a series of technologies with virucidal capabilities with in-depth sheets and technical-scientific evaluations. A final outline summarizes the potential and risks of each method. It emerges that the only technique that is always safe and harmless with the presence of people are purifiers with mechanical filtration – HEPA filters (High Efficienty Particulate Air filter) or even more performing, ULPA filters (Ultra Low Penetration Air).
For each proposed technology, the certifications must be checked on:
– abatement efficiency
– flow rate of the treated air
– any polluting products emitted
June 4, 2021 (change June 4, 2021 | 09:08)
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