Last fall, Jeff Kreiter, director of operational services for the Sioux Falls school district in South Dakota, found himself inundated with proposals to purify the air inside classrooms. The ideas were varied – UV lamps, air exchangers, a wide range of filters – but one seemed particularly promising: a bipolar ionizer. The system involved a set of electrified tubes, placed in air ducts, which would flood buildings with charged particles or ions. Marketing materials from the AtmosAir company promised that it would remove pollutants and viruses by mimicking the ion-rich air found in an alpine village. The district paid $ 2 million to a local supplier to install the system in 33 school buildings. “At the end of the day, we wanted to kill the virus and have a healthier environment, but we wanted that for the long term and not just for corona,” Kreiter says.
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The science behind these ion-producing tubes reads like an elegant example from a high school textbook. The ions are intended to induce what chemists call “coagulation”. Like blood cells that clot in a wound, oppositely charged particles come together, capturing nasty things that you don’t want in your lungs, like pollen and mold. Eventually, these clumps grow large enough that gravity takes over and they fall harmlessly to the ground. With viruses, there is another advantage: the ions erase the surface proteins used to enter cells, making them less effective invaders. The result and the banner claim in the company’s speech to schools during the pandemic, is a 99.92% reduction in coronavirus in 30 minutes.
The problem, according to air quality experts, is that there is little independent evidence to support these claims. Air purifiers are largely self-regulating, with few standards for how manufacturers should test their products, and peer-reviewed research is scarce. Science can work in principle or in a controlled lab test, but how ionization cleans the air in a classroom is another story. Complaints related to Covid-19 are particularly doubtful. Most air filter manufacturers, including AtmosAir, rely on controlled tests that demonstrate how ionization removes viruses found on surfaces, which has little bearing on how ions purify the air.
Frustrated air quality scientists say the industry is playing for money that should go to simpler, proven improvements to school ventilation. “None of these devices have been proven to work,” says Delphine Farmer, an atmospheric chemist at Colorado State University who has studied ionization technology. “Anyone who understands chemistry would say you should be very careful using them.”
A bigger concern, she adds, is the possibility of air cleaning devices getting in the way. Ionizers in particular have a history of producing byproducts, including ozone, formaldehyde, and other volatile compounds, which can damage the lungs. Tests of the AtmosAir ionizer by the New York State Department of Health revealed high levels of ozone in the classrooms where it operated. The company disputes these conclusions and highlights industry certifications that its technology is ozone-free.
But air cleaning is now all the rage in schools, which are receiving federal funds to safely reopen and are poised to receive a lot more. Dozens of districts have purchased ionizers with Cares Act funding, along with other chemical air cleaning treatments. After a quick research, Marwa Zaatari, an air quality consultant in Austin, Texas, came up with a shopping list totaling around $ 60 million. The US bailout package recently approved by Congress includes a $ 122 billion in additional school assistance, arousing optimism from manufacturers and sellers of air filters. “It’s so disappointing that after this sudden realization of the importance of indoor air quality, all the money is invested in unproven technology,” says Zaatari.
The best ways to improve indoor air quality depend on the space, but most experts suggest relatively simple solutions such as opening windows and installing physical filters that meet developed test standards. by organizations such as the American Society of Heating, Refrigerating, and Air-Conditioning. Engineers, or ASHRAE. The acronyms for these standards, such as MERV and HEPA, are a bit confusing, but they reflect what types of particles they can filter out and how fast. MERV-13 filters, which the Centers for Disease Control and Prevention says are effective at filtering aerosols the size that may contain SARS-CoV-2, cost around $ 25. A school may need dozens of filters and eventual upgrades to ventilation systems if it cannot force enough air through the less porous filters.
