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In addition to washing hands frequently and properly, wearing face coverings and practising safe distancing, many people have recently also turned to a product that combines the powers of modern technology and radiation to reduce their risk of contracting the coronavirus.
Yes, I’m referring to UV-C light boxes, which people are now buying to sanitise their mobile phones and even masks. Sanitising the phone makes sense: I mean, we shower and wash our hands but we don’t wash our phone, right? And that makes for an easy attack vector for bacteria, viruses and other pathogens since the petri dish that’s our phone is easily one of the things we touch immediately after we washed our grimy paws.
But do such UV light sanitisers work? Here’s a recap of the science behind it.
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What is UV-C?
Ultraviolet (UV) radiation is part of the full light spectrum and exists across a range of wavelengths ranging from 100 to 400 nanometres.
UV-C, the shortwave UV light that falls in the 200 to 280nm range, is the one we’re interested in because it’s germicidal, meaning it can ‘kill’ germs. Perhaps ‘inactivate’ is a better word because what UV-C really does is to disrupt the DNA and RNA chains of bacteria, molds and viruses. It can also interfere with protein synthesis in some microbes, effectively destroying them.
So, buying a UV-C light sanitising box is as simple as making sure it says ‘UV-C’ on the tin, right? Not quite — here are a few additional buying and usage tips you should know.
Remember this wavelength: 253.7nm
Traditional UV disinfection products mostly used UV mercury lamps, which look like fluorescent tubes. But as technology progresses, many of them — especially small-size applications such as UV-C light boxes — are now using UV-C LEDs.
Regardless of technology, when you’re buying a UV light sanitising device, find out the wavelength its light source is outputting. 253.7nm (often rounded up to 254nm) is the effective wavelength standard germicidal UV lamps use. You may see some sanitisers claiming to be better because their UV-C LEDs have a range of 260 to 280nm — that’s not hogwash because germicidal action is found to reach its peak at around 265nm.
Take note of the number of UV-C LEDs
For safety reasons (warning: never stare or ‘touch’ UV-C light!), most UV-C light boxes can only be turned on after you’ve closed the covers and will cut the light automatically when the procedure is completed or interrupted.
Also, small UV-C light boxes meant for toothbrushes, phones, earbuds, glasses, etc. tend to come with just one or two UV-C LEDs. Personally, two UV-C LEDs are the bare minimum I’ll go for to ensure the item is adequately covered by the light. It goes without saying that the bigger the box — there are those for disinfecting household items, baby toys and even underwear — the more diodes it should be lined with.
Understand the caveats
UV-C light works best when given line of sight, which isn’t something you can always control for phone-sized UV light boxes. This also means that you may want to turn the phone over and run another cycle so that the UV-C light can work its magic on the other side. Some products such as the PhoneSoap Pro have an extra reflective inner shell or coating to help the light reach more parts of the gadget in the enclosed space.
Additionally, UV-C light is most effective on smooth, non-porous surfaces. If you’re using a phone case, it may be a better idea to remove it and clean its nooks and crannies with isopropyl alcohol wipes instead. UV-C light works on masks and fabrics, too; you just have to be aware that it may be less effective due to their porosity and uneven surfaces.
Short cycle times are nice to have
The effectiveness of UV-C greatly depends on the intensity of the light and its distance to the item to be sanitised, with the former tied to the power output of the UV-C lamp or LED and the latter tied to the box’s design (e.g. size, bulb layout).
This is why some boxes take just 30 seconds, some 10 minutes, and some as long 30 minutes to sanitise an item. That said, as long as you follow the instructions, they should be no less effective than what their manufacturers claim. Don’t get me wrong: a UV-C light box with a 10-min disinfecting cycle is definitely appealing, especially when multiple items are queuing up to use it.
Regarding lifespan for UV-C LED-based sanitisers, I’ll consider anything above 6,000 hours to be as good as ‘lifetime’. Remember, those aren’t your living room lights that you turn on for hours every day.
Finally, do your research
Which brings me to my last point: trust. No, I’m not talking about believing UV-C light can kill bacteria and viruses because that’s long been proven by scientists, but rather trusting claims from manufacturers that their UV-C products can do the same thing.
To avoid getting a lemon, I recommend buying from reputable manufacturers, especially those that have prior experience in the UV light sanitiser market. In recent months, many consumer electronics and accessories makers have also started to make these equipment; and while I don’t think these are any less trustworthy, I definitely give higher marks to those that can produce independent lab reports to back their claims.
Also, you’re unlikely to see claims today that these sanitisers can kill SARS‑CoV‑2, the coronavirus responsible for the COVID-19 disease, because UV-C’s effect on this strain isn’t fully determined yet. So be careful if you come across any overzealous claims.
Here are some UV light sanitisers you may want to get for yourself or for your friends.