Caution to the Wind

Brandon Armbruster just wanted to keep his students safe. The chief operating officer of St. Andrew’s Episcopal School in Austin, Texas, Armbruster spent the spring and summer of 2020 diligently preparing for students to return—designing outdoor classrooms, setting up testing routines, and debating whether to cancel sports. A private school with nearly 1,000 K–12 students on two campuses, St. Andrew’s had its own advisory committee of doctors and scientists to guide decisions about COVID. And as they learned more about how the coronavirus could hang suspended in aerosols for hours, the committee urged Armbruster to turn his attention to ventilation and ways to maximize the amount of fresh air St. Andrew’s could pump into its classrooms.

So when a contractor the school had worked with before suggested installing high-tech devices in air ducts to scrub out the coronavirus, Armbruster was intrigued. The devices used a technique called bipolar ionization, shooting tiny, electrically charged ions into the air, where they would interact with and neutralize airborne contaminants like viruses. Or, at least, that’s the theory. According to the manufacturer, Plasma Air, the Spanish Ministry of Defense had backed research that proved its purifier could reduce 99 percent of a coronavirus surrogate from the air in a Madrid hotel room within 10 minutes. All St. Andrew’s would need to do was attach Plasma Air’s small cartridges into its air ducts, hook them up to some electricity, and let the ionization process begin.

Armbruster, a 45-year-old business and finance guy, liked how the ionizers sounded more “proactive” than filters, which trap tiny contaminants as they float through air ducts or are sucked into the kind of free-standing air purifier you can buy at Home Depot. The contractor assured him that other Texas schools had already gone ahead with the technology. But Armbruster wasn’t convinced. For one thing, he couldn’t find much data on bipolar ionization that didn’t come directly from the companies peddling the products. And a video on the Plasma Air website raised red flags. In a science fair–style experiment captured on camera, two slices of bread were placed side by side in transparent boxes—one with a Plasma Air ionizer running, and one without. Over six days, mold blossomed across the bread in the non-ionized box; the other slice appeared fresh. “Yeah, it works great inside a small box,” Armbruster remembers thinking. “But what’s it going to do for a big classroom?”

To find out, he got in touch with Atila Novoselac and Pawel Misztal, two engineering professors and indoor air experts at the University of Texas, Austin. He asked if they would run tests on a couple of these ionizers before the school forked over more than $100,000. “Well, why not?” Novoselac recalls answering. They didn’t have access to a biosafety lab where they could test the ionizers against actual coronavirus. But they could measure whether the machines removed particles or broke down volatile organic compounds released in the air by household cleaning products, which would give them an idea of whether they worked as advertised. “We were quite excited initially,” Misztal says, “because we thought, ‘Wow, if this is really true, with those bold claims that the company was making, that should really help schools.’”

Yet when they turned on the ionizers in their own stainless steel chamber, the two engineers couldn’t detect any meaningful change in air quality. At first they thought the devices must not be working. After consulting the manual and running the tests again, they got