Virus trackers
UofSC scientists model how the COVID-19 virus might travel, settle in indoor environments
Posted on: October 15, 2020; Updated on: October 15, 2020
By Chris Horn, chorn@sc.edu, 803-777-3687
In this age of COVID-19 concerns, what’s the safest indoor environment? One without humans, of course.
But in a practical world the question is especially relevant. The answer lies partly in understanding how the virus moves and where it lands in indoor spaces because air flow and surfaces are important routes for transmission of COVID-19.
That’s why Shamia Hoque, an assistant professor of civil and environmental engineering, and Qian Wang, a professor in chemistry and biochemistry, are developing an experimental protocol to model how indoor conditions influence where virus particles deposit, adhere and persist. Their research, funded by the Office of Research, could have implications for building design and surface finishes and, more immediately, our ventilation system upkeep and housekeeping protocols.
“The general idea is to see what happens when a virus is released inside and where it travels and what happens to the virus particles when they land on surfaces,” Hoque says.
Hoque and Wang will use a measles virus that’s been stripped of its virulence as a
stand-in surrogate for the COVID-19
virus in an indoor simulation chamber. They’ll pay particular attention to how the
virus when released as a simulated sneeze moves in response to air movement patterns
associated with ventilation, changes in temperature and humidity. They’ll also determine
where the virus settles and how strongly it adheres to particular surfaces.
“We want to see if there are air flow conditions near the surface that cause the particles to deposit or instead become airborne again. We want to see what happens once it lands on a surface. It might not stay there; it can go airborne or get transferred to your hand,” Hoque says. “Human activity can move the virus particles from one place to another. It’s important when we’re talking about an infectious virus to know exactly what’s happening.”
Simple physics explains the basics of how particles travel, Hoque says. When the air is humid, droplets that carry the virus tend to be larger and, therefore, heavier, which translates into less mobility. When the air is cooler and drier, droplets tend to be smaller and travel further. Gravity and lack of air movement in certain spaces can create dead zones, which, in a building, are where the virus is likely to deposit and persist.
We tend to think if you clean all the surfaces, you’re safe. But if the air filter hasn’t been changed in 10 years, you’re not doing yourself any favors.
Shamia Hoque, assistant professor, civil and environmental engineering
But Hoque’s and Wang’s research delves much deeper than simple physics. They’re looking at the boundary layer — the airflow that occurs just above a surface — as well as shear forces and surface characteristics to determine their effect on virus particle deposition. Their modeling chamber will mimic the sudden blast dispersion of a sneeze and the gentler but steady dispersion caused by heating and cooling ventilation.
Other variables might affect the transport of the COVID-19 virus, Hoque says, including the height of the person whose sneezes, coughs or just plain talking might be dispersing virus-laden droplets. Kindergartners, for example, are closer to the ground, so droplets emitting from their mouths would likely end up on the table or floor more quickly than those coming from an adult.
Ultimately, Hoque hopes the research could help inform protocols for healthier spaces in office buildings and schools and point the way toward design that will account for infectious disease transmission such as modifying or adjusting ventilation approaches and selection of finish materials less likely to harbor the virus. Addressing those concerns might also mitigate the risk of more common viruses such as the seasonal flu.
“We tend to think if you clean all the surfaces, you’re safe. But if the air filter hasn’t been changed in 10 years, you’re not doing yourself any favors,” Hoque says, adding that the ideal indoor environment in light of COVID-19 would include windows that open. “And having enough space to allow people to spread out would be nice, too.”
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