FEATURE LIGHTING AND ILLUMINATION
Putting UV Covid-19 disinfection under the spotlight
Spectroradiometry can help producers and users ensure UV- based virus-fighting equipment really works, finds Andy Extance
R
obert Yeo first became concerned about attempts to use ultraviolet (UV) light to fight coronavirus on 5 June last year. That day
he took his car to be serviced – the first day the UK’s anti-coronavirus lockdown restrictions were lifted sufficiently to allow it. ‘The garage proudly took my car keys off me, put them inside this UV light box and said, “There you go, you’re safe now,”’ Yeo recalled. They also told Yeo, director at Pro-Lite Technology, that engineers would disinfect his steering wheel, presumably with a UV light wand, a stick with many UV LEDs embedded in it. As a professional in the optics industry, Yeo therefore asked to see the device’s specifications. ‘They showed me, and nowhere did it talk about irradiance and dose,’ Yeo explained. UV wands in particular, which users can wave briefly over a surface without delivering a sufficient light dose, Yeo strongly suspects, are ‘no better than toys’. This situation reflects that, even as
vaccines are successfully deployed in some countries, the world remains desperate for better solutions to the pandemic. Yeo highlighted that UV light – specifically the UV-C part spectrum, that extends from 100 to 280nm – has great potential to fight the coronavirus. Previously 254nm light – a traditional UV disinfection wavelength originating from mercury discharge lamps – had been shown to inactivate the Sars virus by damaging its genetic material1. But it
10 Electro Optics March 2021
Ocean Insight is developing a UV version of its WaveGo handheld spectrometer that can pair with a user’s phone for simple data interpretation, reading and storage
can also damage human cells, Yeo stressed, with longer UV-C potentially causing damage to skin and eyes. As such, users need to be sure that all products work and are safe. Spectroradiometry offers a way for vendors and users alike to have more confidence in their technology – or show, in some cases, that Yeo’s worries are justified. UV disinfection is a well-established
technology, explained Jill Fowler, director of sales at International Light Technologies (ILT), based in Massachusetts, who added that the most effective wavelengths for killing pathogens are from 250 to 280nm. ‘Recent studies have shown promise that both 222 and 405nm are safer to use,’ she
said, including against Covid-192. Low pressure mercury lamps are the
lowest cost source, Fowler continued. However, other sources like UV LEDs and far UV-C excimer lamps have other benefits. ‘The advantages of UV-C LEDs include that they do not emit ozone, use less power and do not contain mercury,’ Fowler said. ‘Such LEDs have a longer life, and they have a conveniently small form factor.’ However they do cost more, especially in the traditional 260-265nm range. Meanwhile, excimer lamps rely on a krypton/chlorine gas mixture and come both with and without UV-B and UV-A blocking filters, which ‘have a great impact
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