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Open those school windows to help stop the spread of coronavirus, experts say

Serbian schoolchildren wearing protective masks on the first day of school Tuesday.ANDREJ ISAKOVIC/AFP via Getty Images

Experts on healthy buildings from Harvard are emphasizing the benefits of opening windows and doors of classrooms to get the air flowing and help keep children, teachers, and staff safe from the coronavirus.

The experts say that the improved airflow can dilute virus particles that may be floating around, looking to make people sick.

Opening windows and doors is “the simplest and quickest way to increase the air-exchange rates,” the experts from the Harvard T.H. Chan School of Public Health said in a recent op-ed in The Washington Post.

“It may sound too simple to be true … But in this case, simplicity is elegant — grounded in science and risk-reduction principles. It’s science distilled to actionable measures,” said the authors, Joseph G. Allen, director of the Healthy Buildings Program at the Chan School, Memo Cedeno Laurent, associate director of the program, and Jack Spengler, a Chan School professor.

One way to test ventilation is to increase the level of carbon dioxide in a room and watch it decay. Here is a graph showing the decay in one classroom with windows closed and with windows - and then a door - opened. The door is opened 7 minutes into the test.Harvard Healthy Buildings Program

Opening windows is one of the tactics suggested in a guide released by the Healthy Buildings program that outlines ways for schools to test, and improve, classroom ventilation.


The importance of opening windows is “100-year-old knowledge,” Laurent said in a telephone interview. “All these things were discussed right after, or during, the Spanish flu pandemic” of 1918.

Schoolchildren in Kyrgyzstan wore masks on the first day of school on Tuesday.VYACHESLAV OSELEDKO/AFP via Getty Images

The goal, the experts said, is five complete air changes per hour, or more, in a room, a standard that most schools haven’t been meeting.

Other recommended tactics to improve ventilation include upping the amount of fresh air brought into the building’s ventilation system, upgrading the filters on the ventilation system to a MERV-13 rating so they can better capture virus particles, and placing portable HEPA air purifiers in classrooms.

Laurent said the experts are also recommending that teachers and students, whenever they’re inside, wear masks as a defense against the virus.


Laurent said that it might be infeasible in some parts of the country, as it turns colder, to keep classroom windows open. But he said that opening them this fall could give schools a chance to check their ventilation systems and implement other solutions.

School districts around Massachusetts have developed a host of different plans to deal with education during the pandemic, including in-person, hybrid, and remote-only instruction. All districts are required to let families opt out of in-person teaching and keep their children home.

Making sure the air in classrooms is clean when kids return is just one of a host of recommendations detailed in a Healthy Buildings Program report issued in June, Risk Reduction Strategies for Opening Schools.

Other recommendations include everything from asking people to wear masks and clean surfaces, to installing plexiglass barriers in some settings, to “reimagining” music and theater classes, to changing arrival, departure, and transition times in hallways.

The Healthy Buildings Program has released other tools intended to help make the return to school safer, including a document suggesting 20 questions parents should ask before sending their children back to school; and a downloadable calculator to help determine how big a portable air purifier a classroom might need.

Felicia Gans of the Globe staff contributed to this report.

Martin finucane can be reached at martin.finucane@globe.com