Windows are liberating. The person in the room can decide how much air and light to let in. So I have never liked when central planners who control buildings omitted windows that could be opened. Other things equal, let people choose. Florence Nightingale wanted open windows, partly based on the mistaken miasma theory of disease. John Snow famously and courageously showed that cholera was caused by bad water, not bad air, thereby jump-starting the process of experts rejecting the miasma theory. But although the miasma theory was not universally applicable (some bad things spread in ways other than the air) and was wrong in some details (what was bad about some of the air was not the air itself, but the pathogens in the air), some of the actions that had been taken on the basis of miasma theory had positive effects. Ventilation was good because the air did sometimes have something bad in it–bacteria and viruses. Closing up buildings kept the bad inside to spread and infect. So now, fortunately, we are back to recognizing that ventilation has important good effects. In the meantime less harm would have been done if our buildings and our other rules had allowed more individual liberty to choose (windows that could be opened), and less centrally planned mandates (windows sealed closed).
(p. D1) One of the paramount lessons of the Covid-19 pandemic is that fresh air matters. Although officials were initially reluctant to acknowledge that the coronavirus was airborne, it soon became clear that the virus spread easily through the air indoors. As the pandemic raged on, experts began urging building operators to crank up their ventilation systems and Americans to keep their windows open. The message: A well-ventilated building could be a bulwark (p. D5) against disease.
It was not a novel idea. More than a century ago, when infectious diseases ravaged cities in the United States and Europe, public health reformers preached the power of good ventilation, and open-air homes, hospitals and schools sprang up in New York, London and other locales on both sides of the Atlantic.
But over the last century, society lost hold of that idea. Scientific advances turned pathogens into problems that could be solved at the individual, biomedical level, with medicines and vaccines, rather than through infrastructure or societal change. Skylines became crowded with air-conditioned towers. An energy crisis encouraged engineers to seal structures tightly. And by the time the coronavirus arrived, Americans were spending their days in schools, offices and homes that could barely breathe.
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Germ theory had not yet gained widespread acceptance; instead, the longstanding theory of miasma held that disease was the result of “bad air.” So sanitary reformers began calling for an overhaul of urban spaces, including improvements in ventilation. “An abundant supply of fresh air, at a proper temperature, is the first requisite of health in every place,” the Citizens’ Association of New York wrote in a report published in 1865.
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Similar reforms were also underway in hospitals thanks, in part, to the crusading work of Florence Nightingale, the British nurse who was stationed at a filthy military hospital during the Crimean War in 1854. The nurse, who believed in the healing power of “air from without,” helped popularize pavilion-style hospitals, which featured long, narrow wards with a row of large, open windows running along each wall.
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Ventilation rates fell and then plummeted further during the energy crisis of the 1970s, when buildings were sealed even more tightly. “In fact,” said James Lo, an architectural engineer at Drexel University, “a lot of effort pre-Covid is to try to reduce the amount of ventilation because people don’t want to spend the energy.”
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In the United States today, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, or ASHRAE, sets widely used indoor air quality standards and specifies minimum ventilation rates. In practice, these rates typically govern how buildings are designed, rather than how they are operated day to day, and many structures deliver less fresh air than they were designed to provide, experts said.
The standards define acceptable indoor air quality as air that does not have “harmful” levels of “known contaminants,” and with which at least 80 percent of occupants are satisfied. But infectious disease is not a focus.
“It says nothing about, ‘Does this level of air quality protect you from risk of infection when the seasonal flu is going around, or when there’s a novel epidemic disease, like Covid?’” said William Bahnfleth, an architectural engineer at Penn State University and the chairman of the epidemic task force at ASHRAE.
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(Note: the online version of the story was updated June 23, 2023, and has the same title as the print version.)