If you have ever lived in a home with an old-fashioned, cast iron radiator, you know how quickly they can turn a home from frigid to a hellish, sweltering oven in less than half an hour. If you have, you probably flung open windows, fiddled with thermostats, or stripped down to your underwear and sweat through the night wondering how supposedly brilliant engineers managed to make a heating system so incapable of moderation.
You're also almost certainly not old enough to remember the 1918-1919 Influenza pandemic that swept across the globe, killing an many as 50 million people and sickening hundreds of millions more — even though you can draw a direct line between your unbearably overheated New York City apartment in 2021 and this public health crisis over a century ago.
The 1918 Influenza Pandemic
In March 1918, just as World War One was coming to its awful, bloody end. Soldiers in the United States started coming down with a relatively mild respitory illness. At Camp Funston, Kansas, 1,100 troops out of 54,000 were hospitalized with this flu, and 38 died as a result of pneumonia. It isn't known if this original strain of H1N1, the Influenza virus, originated in the United States in 1918, but it is almost certain that US troops crossing the Atlantic to join the fighting in Europe brought the flu with them.
By May, it is estimated that three-quarters of the French and up to half of the British troops stationed on the continent had come down with this more mild strain of H1N1. Soldiers suffered from high fevers, body aches, and other typical flu symptoms for around three days before recovering, but given the atrocious bloodshed and loss of life in the trenches, three days off the line to recover from the flu likely felt more like an answered prayer than a dangerous infection.
However, somewhere amid the misery of wartorn Europe, the flu was mutating into a far more deadly strain. In August 1918, British ships left Plymouth, England and traveled to France, the US, and West Africa. Unknowingly, they also carried and spread this deadlier strain, which was capable of killing seemingly healthy adults between the ages of 24 and 34, as well as the very young and the elderly, within 24 hours of the first symptoms appearing.
In the month of October 1918, 195,000 people died in the US alone, but with the war in Europe still raging, officials in the US and Europe were hesitant to put public health measures in place that could harm the war effort, leaving the civilian population at the mercy of the virus, and leaving doctors and public health officials to look for ways to stem the disease.
Our understanding of disease in 1918
By 1918, medicine had come a long way from the days of trying to balance the humors through bleeding and other ghastly practices. Louis Pasteur, Joseph Lister, and Robert Koch, among others, had advanced modern germ theory to the point of general acceptance by the 20th century, but certain outdated medical ideas still held firm — in part because they weren't totally wrong.
One such idea was that disease was caused by "bad air" and poor ventilation, and the best way to slow or stop the spread of an infectious disease was to let in as much free-flowing air as possible to clear out the bad stuff and replace it with the good.
The major proponent of this theory, according to Bloomberg, was Louis Leeds, a former Union Army health inspector who oversaw field hospitals during the Civil War. Leeds came to see "vitiated" air, that which is exhaled by people in confined spaces, as the cause of many number of illnesses. He believed that this "spent breath" was at least in part responsible for nearly half the deaths in the United States.
Another major proponent of this theory was Harriet Beecher Stowe, author of Uncle Tom's Cabin. Writing in The American Woman's Home, a book co-authored with her sister Catherine. The Stowe sisters claimed that, "tight sleeping-rooms, and close, air-tight stoves, are now starving and poisoning more than one half of this nation."
They didn't stop there, describing in sensational terms the effect of vitiated air on young children:
Little Jim, who, fresh from his afternoon’s ramble in the fields, last evening said his prayers dutifully, and lay down to sleep in a most Christian frame, this morning sits up in bed with his hair bristling with crossness, strikes at his nurse, and declares he won't say his prayers—that he don't want to be good. The simple difference is, that the child, having slept in a close box of a room, his brain all night fed by poison, is in a mild state of moral insanity.
In America, the idea that proper ventilation was tied to good health goes back at least as far as Benjamin Franklin, who regularly advocated taking "air baths" where one would sit naked in a room near open windows. Writing to Dutch physiologist Jan Ingenhousz in 1785, he explained that, "I am persuaded that no common Air from without, is so unwholesome as the Air within a close Room, that has been often breath'd and not changed."
By the turn of the 20th century, many had been won over by the so-called "Open Air Movement" and began to work ventilation into the designs of tenement housing, hospitals, and other public buildings. There were even open air schools for children to help combat tuberculosis. Perhaps most important of all were laws like the New York State Tenement House Act of 1901, which mandated that every room have a window facing outside, to ventilate the living space.
While these proponents of "pure air" got the science of disease transmission mostly wrong, proper ventilation is in fact critical to stopping the spread of respitory infections. The issue isn't stale air, but aerosolized water droplets that infected people exhale while coughing, sneezing, talking, or even just breathing. Proper ventilation of indoor spaces is essential for keeping these droplets from being inhaled by others and spreading the infection.
What many in the Open Air Movement attributed to air quality was in reality the spread of airborne pathogens, but in either case, medical professionals knew that ventilation could dramatically reduce the spread of respitory diseases like tuberculosis. So when the 1918 flu pandemic swept over the world, for many, open air treatment was the only treatment they were going to get.
How those Obscenely Hot, Cast Iron Steam Radiators Helped Fight Influenza
When the Influenza Pandemic of 1918 hit, open air and ventilation were still the best public health options for a virus with no vaccine and no access to medicines to treat secondary infections like pneumonia. Indoor public spaces were closed and people were encouraged to go outside as much as possible. But in many parts of the US, the far deadlier second wave of Influenza that hit at the end of 1918 came at a time when temperatures were plummeting, and keeping all of your windows open in the dead of winter was as likely to kill you from hypothermia as it was to save you from the flu.
In order to combat this, buildings started installing centralized heating and cast iron radiators underneath windows. These were designed to run hot enough that all of the windows of a home could be open on the coldest days of the year and the temperature would remain comfortable inside while still providing proper ventilation. Put another way, these old-school radiators can only be comfortable if all of your windows are open, that's how they were designed to be used.
Once the pandemic passed and the Open Air Movement gave way to more modern antibiotics, vaccines, and other medicines, the purpose of these radiators faded from people's minds and subsequent generations all started wondering why their homes became so unbearably hot when the centralized heat was turned on.
It turns out, opening the windows to cool your overheated apartment isn't a response to a defect in your heating system, it's exactly what you're supposed to do, we just completely forgot all about that. At least until 2020, when another respitory pandemic reminded us all about ventilation, confined spaces, and how engineering and architecture is an often overlooked tool in managing a public health crisis.