Linsey Marr’s expertise on the airborne transmission of infectious diseases continues to be in high demand, and her latest foray on the national scene came March 29, when she participated in a virtual event sponsored by the White House Office of Science and Technology.

The event, “Let’s Clear the Air on COVID-19,” focused on the importance of indoor air quality as a means for reducing transmission risk of COVID-19 as well as a tool for fighting the spread of other airborne diseases and pollutants. Marr, the Charles P. Lunsford Professor in Civil and Environmental Engineering, was one of five experts in the fields of public health, social sciences, engineering, and journalism to participate in the hour-long event. 

COVID-19 and other viruses emanate when people speak, cough, or sneeze, Marr and the other experts noted. These actions disperse tiny droplets too small to see called aerosols, which carry the virus into the air.

“They’re small enough that they can float around in the air for a long time,” Marr said. “They’re about the same size as cigarette particles, and they move around in the same way.”

Marr cited three ways that people can take action to reduce the concentration of potentially harmful aerosols in a room or building:

  • Ventilation: This means moving air through a room — bringing in outdoor air that is more likely to be virus-free and pushing out the stale air potentially filled with the virus particles. This dilutes the amount of virus in the room, thus reducing the amount that people indoors are likely to breathe. “This can be done through something as simple as opening windows or adjusting the heating, air conditioning and ventilation system, bringing in more outdoor air and using less recirculated air,” Marr said.
  • Filtration: A portable air machine such as a HEPA unit can reduce indoor aerosols and larger-sized particles such as dust and dander. The machine pulls air through it, and a high-efficiency filter similar to the ones used in hospital settings captures viruses and other particles while pushing cleaner air out the other side. “Filtration is not sieving — or allowing certain things of a smaller size to get through,” Marr said. “HEPA filters are designed to remove more than 99 percent of the particles of a certain size, and people often assume that particles smaller than this size  pass through the filter. Actually, smaller particles are trapped with an even higher efficiency.”
  • Disinfection: Marr said ventilation and filtration should be the first two options considered, but disinfection is also an option for higher-risk areas, such as cafeterias in schools and nursing homes. “Disinfection kills the virus, but doesn’t physically remove it,” Marr said. Hospitals use germicidal UV lamps, which kills off viruses, and there are other emerging technologies.

Learn more about the event online.

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