Andy Larsen: Not many folks wear masks anymore, so here are other effective ways to reduce the spread of germs

Ventilation and air filtration work, CDC studies show, sometimes better than face coverings.

(Phil Sears | AP) At far left, an Aerobiotix air purifier is at work on the floor of the House of Representatives Tuesday, March 2, 2021 during Opening Day at the Capitol in Tallahassee, Fla. Studies show air filters and ventilation can help reduce the spread of viruses.

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No matter what happens with the coronavirus, or any other disease, over the upcoming months, years and decades, I don’t think we’re going to see widespread mask-wearing in Utah again.

It’s become too political. Needlessly so. Masks work, but they’re highly visible. Wearing one — especially when not forced to — has become a statement about one’s political support, and, in particular, for the party to which most Utahns don’t belong. And Utah’s Legislature, which doesn’t look like it’s going to become less conservative anytime soon, has taken steps to prevent mask mandates again.

It’s unfortunate that a health decision has become politicized, but, well, that’s the reality.

So, given that, it’s worthwhile to look at ways individuals and businesses can protect themselves from getting sick in other ways — methods that might fly a bit below the radar and are unlikely to cause fractious arguments with the community. In particular, the Centers for Disease Control and Prevention has recently released two studies that show how effective preventing the spread of viruses through air filtration and ventilation can be; actually, sometimes more effective than donning masks. Let’s dig in.

Air ventilation — like opening a window

Just keeping a space ventilated can do a world of good in terms of preventing the spread of viruses — COVID-19 or not.

To examine this issue, the CDC compared the spread of COVID-19 in elementary schools in Georgia. Schools there took different approaches to the pandemic, with some overlapping and piecemeal solutions. About two-thirds required masks for teachers and staff; about half required masks for students. About 51% of schools also improved ventilation. Finally, about 1 in 5 schools spaced desks at least 6 feet apart, and 22% put plexiglass barriers on desks.

After tallying what the schools did and didn’t do, researchers then counted the number of COVID-19 cases that occurred at the school, and compared them. So what worked and what didn’t? Here’s the breakdown:

As a strategy, the schools that implemented ventilation improvements saw about a 39% reduction in COVID cases — a larger reduction than having the students or teachers wearing masks, and much, much more significant decline than the strategy of separating desks.

That’s because in a classroom, where students are in the same room for a long time, the disease is most likely to spread via floating coronavirus particles suspended in the air. The threat of short-distance “spittle spread” is much smaller.

What ventilation strategies did the successful schools use? Well, they were really simple. The study says that the largest proportion of these schools mostly just opened windows in the room, kept the classroom door open, or used fans. That allows for an escape for those coronavirus particles that an infected person might unknowingly spout, rather than them lingering in the air for an extended period of time.

Sometimes, it’s that simple. Homes and businesses can keep that in mind regardless of whether masks are used.

Air filtration — using a purifier

Want to take the next step? Air filtration systems can further mitigate the spread of the virus.

The Georgia school study also looked at the impact of air filtration. Some schools used only air ventilation strategies (like opening a window or door), some used air filtration systems while keeping the rooms mostly closed up, and some schools did both.

As you’d expect, the schools that did both were less likely to see virus spread. They saw a 48% reduction in cases compared to schools that did nothing, compared to a 35% drop in cases for those who used filtration alone. (As mentioned above, the schools that used air ventilation alone saw 39% improvements.)

Air filtration can be a complicated thing, though. It’s most effective when the filtration occurs in the building’s heating and cooling infrastructure — those typically move a large quantity of air. But stand-alone filtration systems you can buy off the shelves at big-box stores can also be effective.

That was the finding of another recently released CDC study, which tried to mimic a conference-room, church, or classroom environment to see how the virus spreads. They wanted to find out: How many virus particles in such a room can be removed with air purifiers, and where’s the best place to put them?

It’s a bit of a complicated setup, but here’s what the researchers did. First, they set up four particle expulsion simulators in a room. These simulators, shaped like a human head, are tuned to release virus-equivalent particles and nonvirus particles at realistic rates. They put one at the front of the room, and set the simulator to “talking” mode — essentially releasing nonvirus particles at the rate that a person would when talking to an audience. They then set up three “audience member” particle simulators about 6 feet away. The one in the middle was the “source” — it was releasing virus-equivalent particles at a rate consistent with someone who was breathing normally. Researchers then placed one to the left and one to the right of the source. Those two released nonvirus particles, also at a breathing pace.

A graphic of how the CDC's study of air purifiers worked. Only two purifiers were used at once, placed either in the center of the room, in front and back, or left and right. (https://www.cdc.gov/mmwr/volumes/70/wr/mm7027e1.htm?s_cid=mm7027e1_w)

With me so far? Then, they put two HEPA air purifiers (in particular, Honeywell systems that you can buy for about $200 each) in the room, even trying out different locations. They then tested the virus concentration around each of the nonvirus participants after an hour.

So what did they find? Well, they found that air filtration systems worked, and that the best place to put them was in the center of the room. When the purifiers were put around the edges of the room, virus particle exposure dropped by about 50%. When the purifiers were put in the center, exposure fell by about 65%.

That’s without masks on any of the simulators. It probably won’t surprise you that they tried it with masks, too, and then found 90% reduction in particle exposure with masks and centrally located purifiers. Again, I want to be clear: Masks are generally effective at reducing COVID spread! It’s just that making people wear masks right now can be tough, even in a world with the Delta variant. Other strategies, with or without mask-wearing, can be effective also.


Hopefully you’re relatively convinced by now: Air ventilation and filtration can be effective viral reduction strategies. But how do you best implement them? Obviously, solutions can be different, depending on the size of your room, house or building. So what should you do?

For more information, I suggest checking out the recommendations of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, or ASHRAE for short. The group has compiled guides for a bunch of situations — from residential homes and apartment buildings, to schools and commercial buildings. Just click on the topic you’re interested in on their infographic here.

Masks are important, but they’re not the only way to mitigate the spread of viruses. Now, hopefully, you know ways to protect yourself and people you care about without necessarily having to conduct a verbal sparring match.

Andy Larsen, one of The Salt Lake Tribune’s Jazz beat writers, doubles as a data columnist. You can reach him at alarsen@sltrib.com.