Yes, the global heartthrobs are hawking Coway’s air purifiers, a category that’s grown so hot, celebrity air ambassadors are now a thing.

The Great Reopening is officially underway, and schools and offices everywhere are trying to improve indoor air quality in hopes of preventing future lockdowns. In most cases, that means retrofitting tired HVAC systems, installing filters that can catch airborne COVID, and buying air purifiers. 

The result is a huge increase in the global market for residential air purifiers. From 2021 to 2026, it’s expected to grow $46% to $14.1 billion, according to research analysts Markets and Markets. 

Seeing a big business opportunity, startups now offer a long menu of air purifiers—plant-based purifiers; ones that filter out feline COVID; purifiers with vegan-leather straps; purifiers with apps that monitor indoor air quality; wearable purifiers, and so on.

Established players have doubled and tripled their staff. “We’re still observing record-breaking sales in 2021,” says Carolyn Lee, senior brand marketing manager at Coway, noting the company sold more air purifiers in August 2020 than all of 2017. 

Pleasanton Unified School District, in the suburbs east of San Francisco, chose air purifiers from EnviroKlenz, purchasing 800 of their $799 units, each equipped with a high efficiency particulate air (HEPA) filter that captures bacteria and viruses, including COVID, and kills them using UVC bulbs. The purifiers are about the size of a side table. “They’re surprisingly quiet,” says district spokesperson Patrick Gannon, who said that noise was a big concern for the district. 

In whisper mode, filters produce sound that’s equivalent to an electric toothbrush. In high mode, the unit’s 62 decibel hum is grating. There’s one per classroom across Pleasanton’s 15 campuses. Air purifiers are not a requirement of reopening, Gannon says, “but [they’re] part of making parents feel good.” They’re also a quick and easy fix. For comparison, Pleasanton’s budget for its ongoing roof and HVAC upgrades is $62.8 million (commercial HVAC systems cost around $25 per square foot of room space they pump air into and out of).

U.S. schools have access to funds courtesy of the $122 billion American Rescue Plan, which encourages updating ventilation to reduce COVID risk.

Parental oversight is an ongoing problem for most school officials, with some especially worried parents outfitting their children with CO2 monitors, roughly the size of a Nintendo Switch, to provide them a real-time guide of classroom air quality. To be sure, high CO2 levels do not correlate to high COVID levels. But it does signify poor ventilation, which affects students’ concentration and health, in addition to increasing the transmission of COVID and other airborne nasties. 

Since COVID, California and Nevada have made wall-mounted CO2 monitors a legal requirement for schools. CrossFit gyms COVID guidelines recommend that affiliates purchase CO2 monitors. Some HVAC systems deploy CO2 sensors, using the data to adjust building ventilation. The global market for CO2 monitors is forecast to reach $870.6 million by 2027, a 91% increase from 2020. 

Given the stresses of the pandemic and the ever-changing reopening rules, providing parents with peace of mind was a priority for Pleasanton’s Gannon. Since August, Pleasanton’s schools have operated at full capacity. Masking indoors and outdoors is mandated for elementary and middle schoolers, as are classroom and cafeteria seating charts (for contact tracing purposes). The district is more flexible with high schoolers, Gannon says, given the 98.7% vaccine rate of eligible students.

Pre-pandemic it’s fair to say that few people expended much gray matter worrying about school air quality, bar wildfire season in the West. Many American schools have coexisted with exceedingly poor air quality for decades—with data linking this to an increase in asthmatics and lower test scores.

“Everyone deserves healthy indoor air,” says Paula Olsiewski, a contributing scholar from the Johns Hopkins Center for Health Security. Good ventilation is key. Germicidal irradiation via ultraviolet bulbs, as is commonly found in hospital HVAC systems, is a bonus. 

Air purification systems work, she says. But even so, users must account for room size and occupancy. (Harvard University has an online calculator to help schools figure this out.) The goal is for the purifier to cycle through all the air in a room six times per hour, Olsiewski says. “[That way] every 10 minutes the air is effectively refreshed in the room.”

The higher the refresh rate, the lower the risk. She says air quality, until COVID arrived, had an awareness problem. “People understand we don’t drink dirty water [we purify it]. But they have trouble understanding re-breathing the air of someone who’s breathing out COVID.”

Florida-based EnviroKlenz has installed 150,000 purifiers across the U.S. since March 2020. “Growth has been astronomical,” says George Negron, an air quality expert for EnviroKlenz: easily “300%.” Its clientele includes companies trying to get workers back to the office, along with dentists and small-business owners, “down to the mom-and-pop shops that just want to do right.” Looking to 2022 and beyond, Negron predicts that mounted-air purification systems will become integral to new construction—it’s a feature people are looking for, he says.

For now, there’s a lot of hot air in this space, which has real-time consequences. Philadelphia schools blew $4.5 million on 9,500 “developed for NASA” purifiers, which turned out to have low air exchanges and emit asthma aggravating particles. Newark, N.J., spent $7.5 million on Odorox purifiers—considered potentially hazardous ozone generators by the California Air Resource Board, a clean air agency under the auspices of the state’s EPA department.

Multiple brands promoting HEPA-like, HEPA Ultra, HEPA-style, and 99% HEPA air cleaners, which do not meet the standard and can worsen air quality, have made their way into schools. “People were moving fast, and these folks had some good marketing,” says Negron.

Olsiewski, the Johns Hopkins contributing scholar, is dismayed by these snake oil salesmen. “There should be some sort of oversight. There really are no standards,” she says. “These devices are not regulated.” She’s open to emerging technology, as long as it’s proven in large, real-world studies. 

Numerous purifier brands have reached out to Olsiewski, only to ghost her when she asks for their product performance data. “Usually, I don’t hear back.” Much of the science-y-speak hyped in the glossy product brochures is meaningless, she says. An example: bi-polar indoor air tubes, which convert airflow into positive and negatively charged ions that deactivate airborne viruses. “Bi-polar indoor is unproven technology,” she says. “I’ve seen negative peer-reviewed papers saying it doesn’t work.” 

Still, no filtration system can fully protect someone from catching COVID. People who are especially vulnerable should stay vigilant.