Estimated read time: 4-5 minutes
SALT LAKE CITY – Ultraviolet light sanitizers that promise to kill harmful viruses are selling like hotcakes right now. But can a device selling for as little as $40 pack enough ultraviolet wallop to kill a virus? And if so, is it safe to use?
You can find hundreds of gadgets for sale online, from wands and boxes to lamps and even purifying water bottles. Some claim their ultraviolet light will kill 99.9% of harmful viruses, germs and bacteria in seconds.
UV radiation is classified into three types: UVA, UVB and UVC.
UVC is the most capable of breaking down a virus' DNA in a way that stops it from infecting people.
Hospitals use UVC to disinfect surgical and patient rooms. JetBlue and some other airlines are using it to sanitize passenger cabins in minutes. And UVC technology is popping up in heating and cooling systems to purify germy air inside offices and businesses.
But how effective is the technology when it's contained in a portable device?
Testing the devices
To find out, the KSL Investigators bought three consumer devices that use UVC: Two portable wands — one costing $40 and another priced at $80 — plus a $60 UV sanitizing box large enough to hold a smartphone. We took them to the University of Utah's Electrical Engineering department.
Steve Blair has a Ph.D. in the subject, focusing on harnessing light for use in biology and medicine. He eagerly agreed to help us put these three devices to the test.
First things first, directions.
The instructions for one of the devices read, "Can be used to sanitize sofa, bed stuff, clothes, toothbrush, jewelry, watches mask and more."
Blair instantly saw an issue with that statement.
"With any sort of rough surface or fabric, the UV light doesn't penetrate very far," he said.
UV light only disinfects stuff the light touches. Textured stuff like wood or cloth can create a lot of microscopic canyons and viruses can hide in the shadows.
But even if the light can penetrate, do these light devices even work?
According to studies, UV light is "is highly effective at killing bacteria and viruses … mold and other pathogens," but only if the light's wavelength is between 200 and 400 nanometers.
Blair tested the wavelengths of our three devices by using a spectrometer.
Each gadget we measured clocked in wavelengths with at least 260 nanometers.
The translation for you and me: "The wavelengths used by these devices can disinfect surfaces," Blair said.
Not that you can tell just by looking. Each of our gadgets gave a purplish or bluish glow, but that was their LED bulbs — not the UV light. Our eyeballs cannot see ultraviolet light.
The next test: power or dosage.
Blair hooked up each device to a power meter. The more power they put off, the quicker the bugs will be zapped.
"We're looking at about 200 or so microwatts," he said as he tested our $80 wand. The other two had similar readings, and that's not a lot. In fact, these devices are such low power that disinfection will take much longer than just a simple, quick swipe.
Blair ran some calculations and said for that to be effective you'd have to hold the light within a few inches of the surface for at least 20 seconds. Disinfecting a whole room could take days.
"You want to do a doorknob, something – a really small area, high contact surface – I think these can work," said Blair.
Though so does a disinfecting wipe or good old soap and water, he added.
Be that as it may, all three of the devices do work as advertised.
But are they safe?
The same energy that disinfects surfaces can also damage our eyes and skin. Moreover, UV light is known to cause cancer and even a few moments of exposure can be dangerous.
"You definitely don't want the kids to think this is a toy," said Blair.
Blair said consumers really need to pay attention to the safety warnings.
"Make sure you've got long sleeves. Make sure your hands are covered – that your eyes are covered with glasses, sunglasses, something," Blair advised.
Can these devices we tested, or any such gadget sold to consumers actually zap the COVID-19 virus? The answer right now is 'maybe.'
The U.S. Food and Drug Administration said several studies show UVC effectively inactivates closely-related viruses. But at this moment, there isn't enough published data about the wavelength, dose and duration of UVC needed to kill COVID-19.