Coronavirus News: You may be surprised how viruses can spread indoors

ByDan Krauth WABC logo

Tuesday, August 11, 2020

7 On your Side Investigates: How viruses can spread indoors

Dan Krauth has more on how viruses can spread indoors.

NEW YORK (WABC) -- It's a fierce debate taking place across the Tri-State Area and the country right now, whether students and teachers should be heading back to the classroom and how it can be done safely.

For the first time, we're getting a glimpse of what you can't see in the air -- how viruses spread indoors.

Researchers at the University of Minnesota did a first of its kind study showing how viruses can spread indoors and how filtering germs out of the room can be maximized depending on where the ventilation system is located.

They did various experiments to show how the virus can spread spatially indoors and the possible hot zones for which to watch.

In one scenario, when the teacher is speaking at the front of the classroom and the ventilation system is at the back at the room, the study shows aerosols that the teacher exhaled are spread throughout most of the room.

Even with a strong ventilation system, only 10% of what the teacher exhaled was sucked out of the air.

"That's kind of surprising to us that, percentage wise surprising, showing how important the placement of the ventilation is," said Jiarong Hong, a professor at the University of Minnesota.

That means most of those possible virus-carrying droplets are left covering the walls and surfaces, where they could live for days. Researchers say it shows the importance of cleaning those surfaces.

"The surface disinfection is very important," Hong said.

But they also found where that ventilation system is located could make a big difference. In their research, when the ventilation is located right next to where the teacher is talking instead of across the room, more of what was being exhaled was sucked into the system and out of the room.

Researchers didn't just test classrooms.

When they simulated the inside of a grocery store, they found that when a shopper walked the aisles, 40% of what was exhaled by that shopper was filtered out of the room.

That's three times the amount of the classroom.

They believe it's because the shopper is moving, and that the supermarket aisles help with air circulation.

"When the person is moving around the space, it turns out the ventilation is more effective in moving aerosols," Hong said.

Also, when it comes to standing in an elevator, researchers found a solo rider in the elevator for up to a minute faced a low risk. But if there are other people and you're unable to socially distance inside, they recommend not speaking, claiming it can reduce the amount of contaminants spread in the small space.

All of the scenarios were tested without people wearing masks, and researchers believe conditions will improve wearing one.

However, they said it's difficult to test accurately with people wearing masks because different masks have different levels of protections and air flow.

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