With outdoor gatherings beginning to dwindle down as the weather changes, experts are thinking about how greater numbers of indoor events will affect the spread of COVID-19.
A new study conducted by researchers from the University of Cambridge found that current ventilation systems could make exposure to the virus more likely. Though these systems are designed to create optimal temperatures, they also contribute to the spread of airborne particles that can carry infections.
“As winter approaches in the northern hemisphere and people start spending more time inside, understanding the role of ventilation is critical to estimating the risk of contracting the virus and helping slow its spread,” said researcher Paul Linden.
“While direct monitoring of droplets and aerosols in indoor spaces is difficult, we exhale carbon dioxide that can easily be measured and used as an indicator of the risk of infection. Small respiratory aerosols containing the virus are transported along with the carbon dioxide produced by breathing, and are carried around a room by ventilation flows. Insufficient ventilation can lead to high carbon dioxide concentration, which in turn could increase the risk of exposure to the virus.”
Tracking air flow
To better understand how ventilation can affect consumers’ exposure to COVID-19, the researchers analyzed two primary factors: human exhalation and ventilation types.
“In order to model how coronavirus or similar viruses spread indoors, you need to know where people’s breath goes when they exhale and how that changes depending on ventilation,” Linden said. “Using these data, we can estimate the risk of catching the virus while indoors.”
The researchers assessed how actions like talking or laughing -- both with and without a mask -- can affect air quality. They learned that several variables come into play in indoor settings. For example, though laughing was found to emit the greatest number of potentially infectious particles, opening and closing doors, placement of vents, and increased movement in a space can also increase the risk of exposure to COVID-19.
This is why it’s also important to think about ventilation. The researchers explained that displacement ventilation is one of the better alternatives in large indoor spaces, as this allows hot air -- like exhaled breath -- to be filtered out through the top of the room without the risk of other people breathing it in. Though this is ideal, every space is designed differently, and there’s no way to guarantee that ventilation systems will properly filter out airborne infections.
Masks are working
While ventilation systems are out of consumers’ control, the study also found that wearing a mask is one of the best ways to protect against COVID-19. Regardless of any external factors, masks were found to protect consumers from both spreading or contracting any germs.
“One thing we could clearly see is that one of the ways that masks work is by stopping the breath’s momentum. While pretty much all masks will have a certain amount of leakage through the top and sides, it doesn’t matter that much, because slowing the momentum of any exhaled contaminants reduces the chance of any direct exchange of aerosols and droplets as the breath remains in the body’s thermal plume and is carried upwards towards the ceiling,” Linden said.
“Additionally, masks stop larger droplets, and a three-layered mask decreases the amount of those contaminants that are recirculated through the room by ventilation.”