COVID-19 probably spreads through building ventilation, says Canadian researchers working on HVAC patch


The COVID-19 outbreak in a restaurant in southern China’s Guangzhou city was a puzzle.

The suspect index patient was a visitor to the coronavirus epicenter in Wuhan. But the other eight clients who subsequently tested positive were not seated close enough for the transmission of droplets, and most clients and staff completely avoided the infection.

A team of local scientists finally came to a revealing conclusion about the episode: tiny particles of virus had dampened the currents created by the restaurant’s air conditioning.

For a group of civil engineers at the University of Alberta, the conclusion was not a surprise. In their world, they say, it is well known that building ventilation systems are effective discriminators of viruses and other pathogens, and believe that the bug COVID-19 is no exception.

With a $ 440,000 grant from the federal government, they are currently working on ways in which buildings could modify their HVAC configurations to limit the risk of infection, what researchers call a “non-pharmaceutical” intervention against the disease.

We want to save lives, let’s get straight to the point

“We want to save lives, let’s get right to it,” said Professor Brian Fleck, who is part of the project. “There are so many, many, many buildings … It affects everyone. Billions of people. If we are able to reduce the transmission rate by one percent, that’s a lot of people. “

Engineers’ belief in the importance of building ventilation as a transmitter of the COVID-19 virus is not universal.

The World Health Organization and other public health organizations, citing science to date, claim that the pathogen is spread almost entirely by droplets, heavier particles emitted mainly when infected people cough or sneeze and fall a short distance. Hence the two-meter rule for social isolation.

“The HVAC systems of most non-medical buildings play only a small role in the transmission of infectious diseases, including COVID-19,” said the American Society of Heating, Refrigerating, and Air-Conditioning last month. Engineers.

But Chinese and Australian air quality experts, citing in part the experience of SARS, another coronavirus, argued in an article earlier this month that when the droplets of an infected person begin to evaporate, the resulting smaller particles can indeed become airborne.

They say that passengers confined to their cabins on cruise ships like the Diamond Princess have been infected with air conduits on ships.

“It is very likely that the SARS-CoV-2 virus will also spread by air,” they conclude, urging “all possible measures” to respond, including changes to ventilation systems. “We anticipate that … failure to immediately recognize and recognize the importance of airborne transmission and to take no adequate action against it will result in further cases.”

Then there was the case of the Guangzhou restaurant, detailed in an online journal of the United States Centers for Disease Control recently. The researchers concluded that the flow of an air conditioner moved over three tables, carrying the virus from the infected boss in the middle to the distant table, then returning to the guests closest to the air conditioner.

Heating, ventilation and air conditioning (HVAC) engineers have long known that tiny particles of pathogens can be carried in the air that is circulated, heated and cooled in modern buildings, said Fleck. He highlighted Legionnaires’ disease, a bacterial pneumonia, the first trace of which goes back to a hotel’s air conditioning system.

The particle can stay in the air long enough to pass through the system and exit into someone else’s office

“It has been on people’s radar for a while,” he said. “Someone on another floor sneezes … The particle can stay in the air long enough to pass through the system and come out in someone else’s office. “

There are different ways to reduce the risk, including using filters that capture more of these particles and drawing more fresh air into a system. It is also likely that higher humidity levels – a factor that only some Canadian buildings can adjust – will help kill the virus, said Fleck.

But each of these changes comes at a cost. Adding fresh air may require additional heating or cooling. Heavier filters mean more energy is needed to push air through them. And more humidity can lead to mold, he noted.

“It will make decision-making difficult.”

Funded by the Canadian Institute for Health Research, the University of Alberta project is led by engineering professor Lexuan Zhong and also involves professor of pediatrics Lisa Hartling. It consists of three phases: systematically reviewing air circulation and virus documentation, determining which strategies would be effective, and then performing a detailed audit of all buildings on the Edmonton campus to create a real model of what should be done.

The team hopes to have solid results by the summer of 2021, said Fleck.


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