September 25, 2020

the formula to prevent airborne transmission of the coronavirus in enclosed spaces


The spread of COVID-19 occurs more easily in closed spaces, as different studies on its spread reveal. In addition, given the increasingly proven risk that the virus may transmitted to some extent by air, the most effective prevention formula is: let the air run. So it follows from document on air conditioning and ventilation recommendations for the prevention of the spread of SARSCov-2 that have just been updated by the ministries of Health and Ecological Transition.

The document describes a battery of measures that result in the same idea: the ventilation of closed spaces that have been revealed as the most susceptible environment for the expansion of the new coronavirus. Among them, it requests that, in the workplace, the mechanical ventilation system be used at maximum power for two hours before the entry and two hours after the workers’ departure. He also recommends “opening accessible windows.” These currents that renew the air in the rooms are recommended even though there is air conditioning.

“The world must face the reality of SARS-CoV-2 being transmitted over the air,” said Lidia Morawska, University of Queensland (Australia) researcher, publishing in April his conclusions in Enviroment International magazine: “Based on the upward trend in infections and the basic science understanding of viral spread, we strongly believe that the virus is very likely to be transmitted through the air,” he described in his article. You just had to wait for the results of the ongoing studies to arrive, he concluded.

Once the investigations were completed, Morawska herself led a list of 241 scientists who, after reviewing the conclusions, asked the World Health Organization to recognize this route of contagion. SARS-CoV-2, they said, can travel more than ten meters in microparticles exhaled by humans (aerosols). The organization agreed, a little reluctantly, to include some airborne broadcast as possible. Morawska then claimed in The country that “efficient ventilation” was the way to reduce risk in those crowded, closed spaces that pose the greatest danger of the pandemic spreading.

Spotlights in closed places

The Government confirms that outbreaks have been documented in closed spaces with poor ventilation and a high concentration of people that suggest an air transmission along with the proven transmission routes such as interpersonal and drops, which, it concludes, “air conditioning in buildings reduces the risk that an infected person (…) will spread. ” In any case, good ventilation does not eliminate the usefulness of the mask, hand hygiene and disinfection of furniture, floors and equipment, the guide points out.

Another group of Chinese researchers has documented – in the absence of a definitive review – the prevalence of outbreaks in closed spaces over open ones. Of the 318 sprouts they studied, only one was related to an outdoor space. The authors admit that this “does not rule out transmission in open spaces.” However, despite the admitted limitations of their research, they state that “although this discovery was to be expected, its relevance has not been well recognized by society and policy makers. Enclosed spaces are where our lives and work unfold. transmission of respiratory infections such as SARS-CoV-2 is a covered phenomenon. ”

The regrowth map in Spain has followed this line. The pandemic situation reports from the Ministry of Health show that more than a third of the outbreaks reported since the new normal was inaugurated occur in private meetings or parties. Furthermore, the most serious, with even more than 100 associated cases, are those registered among workers in vulnerable situations and nightlife venues. Precisely, the Prime Minister, Pedro Sánchez, has admitted that the living conditions of these workers, the agricultural seasonal workers, are “deplorable”. The contagion in this sector is more related to the places where they live and how they move when they finish the work in the field than with the time in which they work. The characteristics of nightlife venues mix the two conditioning factors that Morawska mentioned: large groups in closed spaces. Your ventilation should work piecemeal.

Less comfort for more safety

“The most important parameter is air renewal per occupant,” states the document prepared by the ministries. For work centers, and even commercial ones, it is recommended to contribute 12.5 liters per minute per occupant if there are outdoor air treatment units to control the quality of the air that reaches the room. “You can work in two directions: increase ventilation or reduce occupancy.” The analysis also asks that the systems remain connected when the premises are empty and on weekends: “Never below 25%” of the normal air flow.

This measure has a clear counterpart: energy expenditure. After all, maintaining air conditioning equipment 24 hours a day, seven days a week imposes high electricity consumption. As the Executive writes “it should be noted that it is a priority to lower comfort and energy efficiency to a certain extent compared to health during the current health emergency.” Thus, priority is given to safety against infections over “thermal well-being” and energy saving.

As an alternative, it is offered that “with mild and favorable outdoor climatic conditions, alternatives for energy saving in buildings such as free cooling could be promoted [se trata de inyectar aire de la calle si está más frío que el interior en lugar de utilizar sistemas de refrigeración], and the action on the mobile shading elements, so as to mitigate eventual increases in energy consumption “.

All in all, this guide stresses the benefits of opening windows for air circulation: “Although it may generate some discomfort from drafts, or thermal sensation, the benefit of air renewal through cross ventilation has been shown to lower pollutant rates of the stays “.

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