A new study from the University of Central Florida suggests that masks and a good ventilation system are more important than social distancing for reducing the airborne spread of COVID-19 in classrooms. The research, published recently in the journal Physics of Fluids. The research is important as it provides guidance on how we are understanding safety in indoor environments.
In the study, the researchers created a computer model of a classroom with students and a teacher, then modeled airflow and disease transmission, and calculated airborne-driven transmission risk.
The classroom model was 709 square feet with 9-foot-tall ceilings, similar to a smaller-size, university classroom. The model had masked students — any one of whom could be infected— and a masked teacher at the front of the classroom. The researchers examined the classroom using two scenarios — a ventilated classroom and an unventilated one — and using two models.
Masks were shown to be beneficial by preventing direct exposure of aerosols, as the masks provide a weak puff of warm air that causes aerosols to move vertically, thus preventing them from reaching adjacent students.
Additionally, a ventilation system in combination with a good air filter reduced the infection risk by 40 to 50% compared to a classroom with no ventilation. This is because the ventilation system creates a steady current of air flow that circulates many of the aerosols into a filter that removes a portion of the aerosols compared to the no-ventilation scenario where the aerosols congregate above the people in the room.
These results corroborate recent guidelines from the U.S. Centers for Disease Control and Prevention that recommend reducing social distancing in elementary schools from six to three feet when mask use is universal. If we compare infection probabilities when wearing masks, three feet of social distancing did not indicate an increase in infection probability with respect to six feet, which may provide evidence for schools and other businesses to safely operate through the rest of the pandemic.
The results suggest exactly what the CDC is doing, that ventilation systems and mask usage are most important for preventing the COVID transmission and that social distancing would be the first thing to relax. The research is part of a larger overall effort to control airborne disease transmission and better understand factors related to being a super-spreader. The researchers are also testing the effects of masks on aerosol and droplet transmission distance. The work is funded in part by the National Science Foundation.