Experts say some classrooms may need an air purifier

Experts from Harvard University and the University of Colorado have developed a downloadable calculator to determine how powerful an air purifier is necessary to help keep kids in classrooms safe from the coronavirus.

Portable air purifiers are just one part of a multi-layered strategy recommended to keep the air in school buildings safe developed by experts from the Healthy Buildings Program at Harvard’s T.H. Chan School of Public Health.

Memo Cedeno Laurent, associate director of the program and one of the creators of the calculator, said the first steps to prevent airborne spread of the virus are to look into a building’s ventilation system to make sure it is drawing enough fresh air and is outfitted with filters that can screen out the virus, and to look at simply opening windows, which can provide a good supply of fresh, virus-free outside air.

The tool, which is a downloadable spreadsheet, allows the user to fill in such variables as the square footage of the room, the height of the ceilings, the building’s current ventilation rate, and the capacity of the air purifier being considered. It then shows whether the air purifier will be able to meet the standard that the experts recommend, five or more air changes in the room in an hour.

The experts advised people to look at the performance of an air purifier in terms of its clean air delivery rate (CADR), which is how many cubic feet of air per minute it can clean of particles. CADRs differ for different substance. The experts said to look at the CADR for smoke or dust.

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