Open windows and glass droplet screens placed in front of desks significantly reduce airborne transmission of COVID-19 in school classrooms, an analysis published Tuesday by the journal Physics of Fluid found.
Simply by opening windows, the number of virus particles circulating in the air in classrooms can be reduced by 40%, according to the researchers.
In addition, the glass screens decreased the number of microscopic virus particles students spread among one another by exhaling, talking, coughing or sneezing, which is how COVID-19 is passed from person to person.
“Nearly 70% of exhaled … particles exit the [room] when windows are open,” study co-author Khaled Talaat said in a statement.
“And air conditioning removes up to 50% of particles released during exhalation and talking but the rest get deposited onto surfaces within the room and may re-enter the air,” said Talaat, a doctoral candidate at the University of New Mexico, where the research was conducted.
As COVID-19 continues to spread, studying aerosol and droplet transport within different environments can help establish effective measures to contain its spread, particularly in settings such as classrooms, as schools across the United States reopen, according to Talaat and his colleagues.
For this study, the researchers used created a computerized model of an air-conditioned classroom to assess how small particles traveled through the air, and from person to person.
Microscopic particles, similar in size to those found in respiratory fluids with COVID-19, were transmitted in significant quantities — up to 1% of exhaled particles — between students, even at a distance of 7.8 feet, because of air flow, the researchers said.
However, using their model classroom, they found that opening windows increases the particles released from the room by nearly 40%, while also reducing aerosol transmission between people within it.
“The aerosol distribution within the room isn’t uniform, because of air conditioning and … student position within the room affects the likelihood of transmitting particles to others and of receiving particles,” Talaat said.
“In our model, the back corners [of the classroom] are the safest spots,” he said.
In addition, glass droplet screens placed in front of desks significantly reduced the transmission of 1-micron air particles from one student to another, Talaat said.
“Screens don’t stop 1-micron particles directly, but they affect the local air flow field near the source, which changes the particle trajectories [and] their effectiveness depends on the position of the source with respect to the air conditioning diffusers,” he said.
Diffusers are the vents that circulate air around a room.
For school reopenings, based on their findings, the researchers recommend keeping windows open when possible and installing glass screens in front of desks.
Students at higher risk of COVID-19 complications should be seated where they are exposed to fewer particles, which will depend on the air conditioning layout within the room, they said.
The group also stresses the importance of sanitizing hands — even without contact with other people’s belongings — because “particles can be transmitted from one student to other students’ desks or clothes, etc., even when keeping separated by a distance,” Talaat said.
“Given the significance of air conditioning, there is potential for optimization of HVAC systems within classrooms to maximize particle removal, while providing adequate ventilation,” he said.