Qualitaly_123

JUN. JUL. 2021 XIII contagion by droplets, the drops of saliva that remain on hands and surfaces. About a year ago, 239 scientists from 32 countries raised the issue by sending a letter to the World Health Organization. An invitation to consider droplet contagion. In the missive, published in “Clinical Infectious Diseases”, the scholars asked the WHO to revise the guidelines, issuing an alert, saying that even the smallest particles capable of travelling very far in the air can infect people. And thanks to this exhortation, the WHO Coronavirus Technical Group has moved to consider the importance of indoor ventilation. HOW CONTAGION OCCURS The emission of viral load from an infected subject depends on its metabolic and respiratory activity. “An infected person,” says mechanical engineer Michele Vio (Studio Vio, Venice), expert in air conditioning systems, “when speaking, releases a certain number of elementary viral charges, the ‘quanta’, which are able to infect the unvaccinated or auto immune person with a probability of 63%”. A person sitting in silence releases about 0.5 viral charges per hour; if they speak in a normal voice, for example in their office, they release 10 viral charges, if instead they speak loudly, as happens in bars and restaurants, they can release from 60 to 100 viral charges. A study done in the United States at the beginning of the pandemic found that a chorister released between 400 and 500 viral loads per hour while performing.” An experiment that confirms that individual behaviour, such as tone of voice, is absolutely critical in reducing or increasing contagion. We must not overlook the contraction of viral loads within the environment, so, with the same number of infected people, the size of the environment is also fundamental: the larger the environment, the lower the risk of contagion. TECHNOLOGY HELPS In the last twenty years, technology has managed to measure the release of every ‘human act’: from speech to physical activity of all particles, even the finest ones like aerosol, which remain in the air and have no ballistic-type trajectory like a droplet. “The aerosol linked above all to our respiratory act, remaining in the air, saturates the environment,” continues Vio, “therefore it is necessary to take action on the circulating particles in two ways: by increasing the ventilation with external air or by filtering the air inside the environment. Aerial spread of the virus is controlled by diluting or removing the infectious agent from the air volume of the shared environment. To minimize the viral load in circulation and lower the probability of contagion, proper ventilation is essential, but this is not always sufficient, so in some situations it is necessary to intervene mechanically or chemically to remove the viral load from the atmosphere. The ideal solution is to use an air filtering treatment system”. The report from the Istituto Superiore della Sanità suggests the use of air purification and sanitization systems. The report also specifies that ventilation alone does not lower the risk of transmission of the virus, especially in very crowded environments, where people stay for some time, such as in school classrooms or restaurants. Ventilation therefore plays an important role in combating virus infection. It all depends on the number of times the air is exchanged in the environment where one is staying and the time the virus stays in the space. Therefore, the risk of contagion is greater in a restaurant than in a supermarket where the average stop time is about half an hour. Therefore, to minimize the risk of contagion in a restaurant it is advisable to change the air at least 4 times an hour. If this is not possible, action must be taken by installing purification systems. “On the market there are purifiers that, in addition to filters of various types, allow the ionization of the air, that is the destruction of germs and viruses through the introduction of specific molecules,” concludes Vio. The UV lamp, unlike other filters, kills both bacteria and viruses quickly, irradiating them with its light, for a few seconds, which is possible only in the presence of sufficiently long ducting. Alternatively, you can use the Upper-room UVGI, lamps already in use in third world countries and in some hospitals in the USA, which emit UV rays at 250 manometers of wavelength near the ceiling, where the air is quiet, to fight both viruses and bacteria. An effective solution to fight viruses and bacteria but not for improving air quality. This result can only be obtained by creating an ad hoc system that introduces