Doctors and specialists warn of the false security offered by the “bubble terraces”, in which there is little ventilation.

Different clients enjoy a terrace on the Malvarrosa beach in Valencia.

After more than a year of pandemic, Spain is heading towards the fourth wave of the Sars-CoV-2 coronavirus with some uncertainty. Everything seems to indicate that infections will increase in the coming days and that Easter could cause a greater increase in transmission. However, it is no less true that the greater availability of vaccines will allow Spain to accelerate its vaccination plan and increase the percentage of the population immunized against Covid-19.

During these holidays, many people will take to the streets and decide to enjoy a meal in the company of friends and family in bars and terraces before curfew. As everyone knows by now in the pandemic, the safest place for this is a good outdoor terrace. However, not everything we find in front of the bars. These days, some doctors and specialists have denounced that some terraces that install bars and restaurants, covered and protected by tarps on the roof and on the sides, are not exactly a safe place for customers but, rather, “virus incubators” , “Bubble terraces” or, as some have baptized them, “disturbing”.

“The bubble terraces. Everything that should not be done. Everything closed except one entrance ”, denounced through his Twitter account Vicente Baos, family doctor, disseminator and professor of Medical Pathology and Public Health at the Autonomous University of Madrid (UAM). “Incognitous. The hotelier paripé so that customers think they are safe in the middle of a pandemic because They are on the ‘outside’ and warm (although, in reality, it is one more interior space) ”, answered Baos the doctor in Regenerative Medicine and disseminator Esther Samper.

In fact, other experts such as Ignacio Rosell, professor of Preventive Medicine and Public Health at the University of Valladolid, had already warned of the problem that these investments in the hospitality industry represent in the current context. “For the coronavirus this is not a ‘terrace’, but rather a ‘fish tank’, in which it moves like a fish in water. Watch out. I am concerned that in such a difficult year, hospitality people invest in facilities that could later be limited, ”explained Rosell through his Twitter account.

The truth is that, no matter how much we weigh, restaurants are the places where there is a greater risk of contagion. According to a study published in the journal Nature, there is a greater risk than in gyms, cafes, hotels or supermarkets, for example. The reason, as you know, is that these are closed, smaller, crowded places and in those who chat at a short distance and without a mask, so it is much easier for a person to end up inhaling the droplets and aerosols that we expel when we speak.

A few months ago, another study carried out by researchers from the Centers for Disease Control and Prevention (CDC) on a restaurant in the city of Guangzhou (China) warned of the danger posed by air conditioning in premises. The work, published in the magazine Emerging Infectious Disease, demonstrated how a single asymptomatic subject ended up causing an outbreak that affected nine more people from three different families who were on the same floor of the restaurant as him. The transmission of virus particles through recirculation of air conditioning in a closed room was the key.

“Small virus-laden aerosol droplets smaller than five microns can remain in the air and travel long distances of more than one meter,” the study notes. “We conclude that in this outbreak, droplet transmission was caused by air-conditioned ventilation. The key factor for the infection was the direction of the air flow, “the researchers concluded. With the so-called “forgetful” it is practically the same. Is it so far from being safe places Because, precisely, the arrangement of the canvases prevents the air flow from flowing normally. It would be different if these tarps were removed and the terrace was left in the open air.

Some studies have shown that the only way to control air quality in closed rooms is through continuous ventilation and CO2 meters, a tool the latter that has tried to impose itself in different communities with uneven luck. “In the event that the CO2 concentration exceeds 800 parts per million, it is recommended to increase ventilation or decrease the capacity until it falls below that indicator,” says a report from the Government of Navarra. Thus, for the moment, the best thing is still going to a traditional terrace outside, without parapets of any kind, where the risk of contagion, despite continuing to exist, will be much lower.