An essential convenience for people living in the southern states, air conditioning has come under scrutiny for potentially aiding the increasing spread of the coronavirus in areas with an intensely hot summer climate.
With coronavirus cases increasing dramatically in Texas, Louisiana, Florida, and other states in the southern part of the US, researchers and epidemiologists say that more time indoors, sometimes with recirculated air, can be a factor in the spread.
Dr. Edward Nardell, a professor at Harvard University studying airborne diseases, argued in the medical journal JAMA in June that air disinfection was overlooked in the prevention of COVID-19. In an online presentation last week sponsored by the Massachusetts Consortium on pathogen preparedness, he linked an increase in air conditioning use and time spent in the interior of southern states with an increase in COVID infections. -19.
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Nardell said that high temperatures lead people indoors, where the coronavirus can remain for hours. In poorly ventilated buildings with no outside air flow, the virus could be pushed by currents created by air conditioning units. In many modern buildings, energy efficiency allows a small flow of outside air, which could create a high concentration of virus-laden air that is continuously whipped around a room.
Some researchers have echoed some of Nardell’s conclusions, although many point out that the increase in infections probably has more to do with people who do not wear masks or who do not practice social distancing. Still, spending more time indoors with other people may be having an impact, they say.
Viruses generally disappear in the summer, when children are not in school and families spend more time outdoors.
But in the south, extreme heat is common. And for a virus that spreads through airborne droplets, enclosed spaces with recirculated air can be more infectious than well-ventilated buildings.
Outside of New Orleans and some cities in California, the United States’ epicenters for coronaviruses in March and April were found primarily in the northern states, including New York state, Michigan, and Washington. But as cases slowed in those regions due to restrictions and the season moved into spring and summer, more infections have emerged in the south and west.
Texas, Arizona and Florida have released their highest daily case counts this week, with intensive care units in some areas of those states at capacity.
In May Louisiana and New York faced Florida-imposed travel restrictions. Now, things have changed and New York has imposed restrictions that require Florida and other states to be quarantined after entering its borders. The cases are flat in New York, while they have increased in Texas for 22 days and have generally doubled.
Air conditioning, whether hot or cold, is usually the same air recirculated in a building. Many high-efficiency systems supply a small amount of outside air to conserve energy in the new air conditioner. Because the coronavirus can remain in the air, an infected person in an enclosed space can contaminate more air, and then air conditioning units can push that air in a way that exposes more people.
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A small study from Wuhan, China, published in Emerging Infectious Diseases, found that one person infected nine other people in a restaurant, not just those sitting at the same table, but also those on both sides. The study authors noted that the air conditioning unit pushes the same infected air around the room as the transmission mode.
Not all air conditioning increases the likelihood of infection, and it’s only a factor in potentially growing cases, according to William Bahnfleth, an indoor air expert at Pennsylvania State University and chair of the American Heating Society’s epidemic task force, Refrigeration and Air Conditioning Engineers.
The Wuhan restaurant did not have an outdoor air supply, which could contribute to the amount of drops in the environment.
“It allows pollutants in the air to concentrate,” said Bahnfleth. “Imagine that you are cooking and there is a fire, you are turning bad smoke from the stove. You open a window to dilute it.”
While the Wuhan restaurant study was speculative, according to Bahnfleth, it still highlights the risk of unventilated spaces that recirculate air, like many older buildings.
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A connection between the increase in cases in the southern states and the use of air conditioning is also speculative, said Susan Hassig, an epidemiologist from Tulane, who pointed out the general risks of being indoors among people, especially since wearing masks does not it is always mandatory. elected officials and has been transformed into a political statement.
Air conditioning flow patterns in poorly ventilated buildings, without the introduction of outside air, can contribute to infection rates, but the higher rates can also be attributed simply to being indoors after mixing with people outside your ” capsule “quarantined, Hassig said.
“It’s not about people in Phoenix sitting in their air-conditioned homes, it’s about people no sitting in their air-conditioned houses and going out and mixing with other people, “Hassig said.
Transmission of COVID-19 in closed environments can be 18.7 times higher than in an outdoor, open-air environment, according to a report from Japan awaiting peer review.
“That is the idea of why eating indoors is more problematic than eating outdoors,” Hassig said. “It’s not just the air conditioning. It’s the closed air environment.”
Bahnfleth said that most building codes require a level of ventilation that is sufficient to introduce fresh air. For people who work in offices, he recommended consulting with the building manager to make sure the building has outside ventilation. Your organization also recommends upgrading the filters to a denser material, from the standard MERV-8 filter to a MERV-13 filter, which can trap more particles.
Nardell, the Harvard scientist, proposed an ultraviolet light installed near the ceiling of a room, where hot particles expelled from a human body would accumulate, as a way to disinfect buildings. Ultraviolet light has been shown to reduce airborne transmission of tuberculosis by 80%, but it would have to be used with caution because it is a carcinogen.
Overall, proper air conditioning and ventilation is just one of the pieces that, according to prevention experts, will make the difference in infection rates.
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“Air conditioning is a risk in poor ventilation conditions,” said Bahnfleth. “But when you have normal ventilation, the risk is pretty low as long as you do the other things you’re supposed to do. The risk of not distancing yourself and not wearing masks is still the greatest.”
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