One day in March, the kids were there. The next day, there was no one. Then on a Saturday in August, a man came into an empty public school in suburban Boston carrying a container of dry ice, trying to figure out how to bring the students back to their desks.
Since January, that man, Joseph Allen, a professor at Harvard’s School of Public Health, has been saying to anyone who will listen that air—the stuff that everybody breathes and nobody thinks about—has got to move. Before the lockdown, his lab’s whiteboard was dense with notes about how the SARS-CoV-2 coronavirus might spread indoors. Trapped at home, he wrote scads of op-eds, talked to journalists, and was one of the scientists who reviewed an open letter to the World Health Organization demanding that it acknowledge that the virus can be spread through tiny particulates in the air.
With the billowing plumes of dry ice, Allen, his team, and the school’s maintenance employees conducted experiments, measuring the flow of air in various buildings. If Allen has anything to say about it, in some classrooms this fall you might see a fan with a crinkly white HEPA filter strapped to it. In the walls, ventilation systems may be fitted with filters too. As long as the weather permits it, windows will be flung open and wedding tents will be pitched on fields, as school administrations focus on what seems like a simultaneously simple and overwhelming task: Move the air around. Filter it. Dilute it.
While physical distancing and mask wearing help cut down transmission via larger droplets, when it comes to airborne transmission, ventilation and filtration, which reduce the concentration of virus floating in the air, will also be key to making indoor spaces safer.
Allen, who worked as a safe-buildings consultant before entering academia, has been helping schools, universities, and daycare centers work on plans for reopening. “Very often I get the comment, ‘Oh! You’re the first person we’ve heard talk about ventilation!’” Allen says. “That’s deeply concerning.”
The pandemic spotlights a problem that Allen and his colleagues have known about for years, but that most other people have no clue about: Schools are chronically under-ventilated. A commonly used standard for air movement says that, at minimum, 15 cubic feet per minute (cfm) per person should flow into a classroom; Allen says that for Covid prevention, he recommends 30 cfm. But studies show many American classrooms have an average ventilation rate of only 6 to 11 cfm per person.
Even when there isn’t a pandemic going on, that’s not good, because a substantial body of research suggests that better air flow is correlated with increased test scores and reduced absences. At least one study using air filters in classrooms also found increases in student achievement.
The care and feeding of air fell out of public consciousness a long time ago, though. So as fall approached, Allen and his colleagues released a detailed report on how to open schools more safely and provided guidance to those who’ve reached out to them. “The problem is, we’ve lost our way over the years,” Allen says.
It’s taken a worldwide pandemic to get us to pay attention to the air children breathe.
When it came to designing buildings, airflow used to be way up there on the priority list. After much of Britain’s parliament building, the Palace of Westminster, burned in 1834, David Boswell Reid, a doctor, chemist, and inventor, was asked to handle the ventilation of the new building. Members of Parliament had found the old building stuffy, and serious air pollution in London made cracking open a window a risky and extremely unpleasant move. Reid had developed an elaborate ventilation system for his private lab in Edinburgh, and he spent the next few years testing and perfecting his design for Parliament. His plan relied on the natural buoyancy of gases to pull air out of debating chambers and draw fresh air in, and even used wet canvas to filter out pollution. In the temporary House of Commons, he put in an entire ecosystem of ducts that vented air up through flues on the roof. In Reid’s design for the permanent structure, towers that look like Gothic whimsies are, in fact, functional tools for ventilation.
Keeping the air at a comfortable temperature was Reid’s overriding concern, but he also strove to keep fresh air circulating. For much of the 19th century, the prevailing theory was that diseases like malaria or cholera were caused by miasmas, or “bad air.” The theory was invoked to explain why people living near swamps got sick (today we’d probably say mosquitoes) and why slums were festering pits of disease (we’d now put it down to poor sanitation). And yet they were on to something when it came to air movement.
