FEATURE LIGHTING AND ILLUMINATION
completely necessary to assess UV light source safety. ‘It gives more data than a simple radiometer, a light meter filtered to only receive the UV-C part of the spectrum,’ he explained. ‘A radiometer would tell you if there is UV-C radiation or not.’ But UV-C radiometers like the Solar Light range that Pro-Lite supplies predominantly measure the 254nm emission peak originating from mercury lamps. ‘The problem comes if you’re interested in 230nm,’ he said. ‘If you were a manufacturer of a UV-C disinfection device, it’s probably an easy choice between a radiometer and a spectrometer, because there’s not a lot of price difference. Spectroradiometers such as those from Avantes and Jeti, which Pro-Lite supplies, are definitely more expensive, but we’re not talking times 10.’ One reason such instruments are
Radiometers like the ILT770UV can determine whether a disinfection device emits UV light
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will help minimise risk of bad installation, it will group products and detail how they are to be used. Agreeing on nomenclature and classification will help impose clear measures for the industry.’ To ensure safe deployment of UV-C
disinfection, spectroscopy is an essential tool, Stefkova continued. ‘Being able to measure the wavelength when deploying UV-C disinfection systems will aid the safe operation – for effective disinfection, the proper dosage needs to arrive at a surface. Dosage is a calculation of energy over area, and energy is dependent on the wavelength. Knowing the wavelength enables the dosage calculation and potential exposure.’ UV lamps have a limited lifetime, so
not only is it important to control quality during manufacture but during use too, Stefkova added. ‘Hand-held spectroscopy is a tool that can be used on the production line and by the end-user,’ she said. ‘As the regulatory landscape for UV-C is in its infancy, any system should be validated and frequently checked.’ As one option, Ocean Insight’s
spectrometers are accurate and portable, Stefkova said. The company is developing a UV version of its WaveGo hand-held spectrometer which can pair with a user’s phone for simple data interpretation, reading and storage, she said.
Distance reduces irradiance Pro-Lite’s Yeo suggested that spectroradiometry may not always be
12 Electro Optics March 2021
International Light Technologies’ ILT960UV-RAA4 spectrometer can help verify the safety of UV disinfection systems
@electrooptics |
www.electrooptics.com
important is because ‘you can’t assume that an instantaneous exposure is going to have the desired effect’, Yeo continued. Lamp effectiveness depends on irradiance, power per unit area delivered to the surface. That depends on the distance between the lamp and the surface being irradiated in an inverse square relationship, Yeo stressed. As such, doubling the distance quarters the irradiance. ‘That’s not a well understood concept,’ he said. Producers should therefore use tools to quantify performance and provide simple guidance. ‘The manufacturer of the disinfecting product should define the distance at which you hold the lamp over the surface, and how long you should hold it there,’ Yeo said. ‘Lovely looking
‘The manufacturer of the disinfecting product should define the distance at which you hold the lamp over the surface, and how long you should hold it there’
UV light sources that are available very inexpensively might not be at all effective.’ And that’s just what tests have shown. At the ICUDAS meeting Gareth John,
of the UK’s Lighting Industry Association (LIA), revealed results of testing hand- held UV wands. LIA usually offers a service to manufacturers and other companies wanting to test lighting’s optical specifications, John explained. Among its test equipment is an IDR300 photobiological safety spectroradiometer made by UK firm Bentham, which can cover the range from 200 to 1,100nm. LIA has been testing UV Covid disinfection products as a service to interested parties, but also a random sample of seven wands bought from the internet in its own study. ‘We’ve been looking at kill rates of
200J/m2, enough energy to kill 99 per cent of known germs,’ John told Electro Optics. ‘A lot [of devices] didn’t deliver any UV-C at all. Plenty of them were just based on 405nm LEDs, so you get a sort of indigo glow.’ Meanwhile, for some wands that do deliver UV-C, the dose was so weak that it would have taken up to 10 minutes to reach the specified kill rate. ‘These things tend to
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International Light Technologies
International Light Technologies
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