Online calculator weighs risk of airborne COVID-19 transmission in classrooms

By: - August 11, 2020 1:30 pm

An online calculator that teachers, administrators and students can use to estimate the risk of airborne transmission of the COVID-19 virus in classrooms has been developed by researchers at Duke University.

The calculator was created  for college campuses but can be used by K-12 schools to help inform decisions on “school re-openings” and to assess the effectiveness of control measures in classrooms, cafeterias and gymnasiums, researcher said in a news release.

“The idea was to make it as easy as possible for non-scientists to assess the probable risk of COVID transmission from microscopic airborne aerosols containing the virus, which is a newly discovered route of infection,” said Prasad Kasibhatla, professor of environmental chemistry at Duke’s Nicholas School of the Environment.

Here’s how the calculator works:

To calculate a risk of infection, users enter information about the physical characteristics of the room to be used such as its height and floor, the number of students who will be present, and the duration of each in-person class session or school activity – into highlighted fields on the calculator’s webpage.

Prasad Kasibhatla

Clickable links guide users to “how to” pages that help them answer questions that require more technical knowledge, such as knowing a room’s ventilation rate. There’s also a link to a page that explains how community infection rates – a required field – can be derived from current information on COVID case counts in the user’s area.

After data is entered, the model calculates the probable concentration of airborne virions, or infectious aerosol particles, that have been exhaled into the room by someone infected with COVID, as well as the probable concentration, or dose, of these virions that will likely be inhaled by uninfected people in the room, even if they are using protective masks and practicing social distancing.

Click here to use the calculator.

“Our goal was to use advanced science to create a tool that non-scientists can use,” Kasibhatla said. “We can’t predict or eliminate all risks, but using our calculator can help teachers and school officials zero in on which control measures – more ventilation? fewer people? shorter class durations? – might make the biggest difference in their classrooms.”

Researchers said the actual risk of infection from aerosols may be higher than calculated if social distancing, mask use and hygiene protocols are not strictly adhered to in a classroom. The calculator doesn’t measure the risk of COVID transmission by droplets or from contaminated surfaces, two other potential routes of infection.

Kasibhatla developed the calculator with fellow Duke faculty members John Fay, a lecturer in the Geospatial Analysis Program; Elizabeth Albright, assistant professor of the practice of environmental science and policy methods and Bill Pan, the Elizabeth Brooks Reid and Whitelaw Reid Associate Professor of Population Studies.

It’s based on a COVID-19 risk estimator developed earlier this year by Jose-Luis Jimenez, professor of chemistry and Fellow at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder. Jimenez’s estimator assesses transmission risks associated with a wide array of settings and activities.

The study comes as North Carolina prepares to reopen schools Aug. 17. The majority of students will begin the school year receiving remote instruction. Some districts, however, will reopen with a mix of in-person instruction and remote learning.

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Greg Childress
Greg Childress

Education Reporter Greg Childress covers all aspects of public education in North Carolina, including debates over school funding, curricula, privatization, and teacher pay and licensing.