Originally published 2021-02-25.
Photo: Janis Laizans/Reuters
In February 2021 the Estonian start-up Respiray unveiled a wearable air purifier that, according to the company, kills more than 99 percent of the viruses and bacteria in the air its wearer breathes. The battery-powered device hangs around the neck, filters incoming air, passes it through ultraviolet (UV-C) light and then blows it gently toward the face. It went on sale for 279 euros, with the first deliveries planned for March 2021.
The gadget arrived at a moment when people were looking for anything that might add a layer of protection against Covid-19. Here is how it worked, what the tests did and did not show, and how UV-C light really fights germs.
How the Respiray purifier works
The device is a plastic box worn on the chest, with an optional clear face screen that leaves the face visible, an advantage for teachers, shop staff and anyone who needs to be understood or recognised. It works in three steps:
- Filtering. Air is drawn in through a filter that removes dust and larger particles.
- Disinfecting. The air then passes a module of UV-C LEDs designed to inactivate viruses and bacteria.
- Delivery. The cleaned air is directed upward toward the wearer's face.
The design rests on the observation that much of the air we inhale comes from warm currents rising along the surface of the body. By feeding cleaner air into that stream, the company says, the wearer breathes mostly treated air. A charge lasts about eight hours.
The UV-C technology behind the device was developed with researchers at the University of Tartu in Estonia and the University of Lodz in Poland.
What the tests showed, and what they did not
Respiray reported that tests at the University of Lodz found reductions of 99.68 percent for E. coli and 99.88 percent for Staphylococcus aureus bacteria. A University of Tartu study found 99.4 percent effectiveness against an alphavirus, chosen because it is similar in size and structure to SARS-CoV-2, the virus that causes Covid-19.
Liane Viru, head of the Biosafety Core Facility at the University of Tartu, said the small amount of virus left after treatment was
"very unlikely to cause infection in the target organism."
Those numbers are encouraging, but they describe laboratory performance: how much of a test microbe survives when air passes through the device under controlled conditions. They are not the same as evidence that people wearing it catch Covid-19 less often in everyday life. That would require trials comparing wearers and non-wearers, and no such results were published at launch. Real-world performance also depends on fit, movement, wind and how much unfiltered air reaches the nose and mouth from the side.
Estonian officials presented the device as one tool among many. Indrek Reimand, vice-chancellor at the country's education ministry, which planned to give the purifiers to schoolteachers, put it simply:
"There's no magic wand against the virus."
Estonian retailers also ordered the device for customer-service staff.
How UV-C light kills germs
Germicidal ultraviolet light, known as UV-C, sits at wavelengths of roughly 180 to 280 nanometres. It damages the genetic material of bacteria and viruses, which stops them from copying themselves. Hospitals have used it for decades to disinfect surfaces and the upper air in rooms; a 1936 study at Duke University reported that operating-room infections fell sharply after UV lamps were installed.
The key word is dose. How much a microbe is damaged depends on the intensity of the light multiplied by the time it is exposed. Fast-moving air spends very little time near the light source, so a small, battery-powered device has to be carefully engineered to deliver enough exposure. That is one reason independent testing matters so much for this kind of product.
UV-C is also harmful to people. Common germicidal lamps at 254 nanometres can burn the skin and cause painful eye inflammation, and some wavelengths below about 242 nanometres produce ozone, which irritates the lungs. Devices like Respiray's keep the light inside an enclosed module so the wearer is never exposed to it directly. Products that shine UV-C openly onto skin, hands or faces should be avoided.
A purifier is not a replacement for a mask
During the pandemic, health agencies recommended masks mainly because they reduce the droplets and aerosols an infected person breathes out, while also giving the wearer some protection. A neck-worn purifier works differently: it aims to clean the air coming in, and its design does not treat the air the wearer exhales. It may add protection for the wearer, but it should not be assumed to protect the people around them.
Anyone with a lung condition, or anyone unsure what protection suits them, should talk to a doctor rather than rely on a gadget's marketing.
Myth check: UV light inside the body
UV light was in the news for a less helpful reason in 2020. At a White House briefing on 23 April 2020, President Donald Trump wondered aloud whether the body could be hit with "ultraviolet or just very powerful light", and whether disinfectant could be used inside the body "by injection". He did not tell people to drink bleach, as is sometimes claimed, but he did call the idea interesting to test.
The response was swift. The US Environmental Protection Agency, the makers of Lysol, the World Health Organization and other officials warned that applying disinfectants or ultraviolet radiation to the human body is harmful. Several US states reported a rise in calls to poison-control and health hotlines. Trump later said he had been speaking sarcastically.
The difference with devices like Respiray's is fundamental: they use UV-C on air inside a sealed chamber, never on the body.
What became of Respiray
Respiray has since broadened its range beyond the pandemic. Its website now lists the Wear A+ wearable air purifier in versions with HEPA filters for travel and allergies and activated-carbon filters for odours, alongside a UV air purifier and a neck fan. The company presents its products as tested and certified, though its site does not name specific standards or published studies. It now lists a business address in Sarasota, Florida.
For shoppers, the lesson from 2021 still applies to any air-cleaning gadget: look for independent testing, check whether results come from a lab or real-world use, and treat "99 percent" claims as a starting point for questions rather than a guarantee.
Sources: TimesLIVE / Reuters, 23 February 2021; Respiray; Wikipedia: Ultraviolet germicidal irradiation; Wikipedia: COVID-19 misinformation by the United States; original reporting by Reuters. Photo: Janis Laizans/Reuters.
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