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Electrically Produced U.V.C. and disinfection.

Zoomup
U.V. light and bug killing.....

https://www.bbc.com/future/article/20200327-can-you-kill-coronavirus-with-uv-light



Z.
  • 0
    In my days in Royal Mail we used different frequencies of UV light to detect phosphor markings on stamps to sort 1st and 2nd letters and to sort letters to destinations from phosphor dots we imprinted on letters on automatic sorting machines.
  • Former Community Member
    0 Former Community Member
    mapj1:
    123misha:

    is it effective to use UV Light?


    For what purpose - I think your question is missing a bit.

    There are several grades of UV light, for rapid grading A, B and C as progressively shorter wavelength - as already noted above, you ned to know what you are doing. There is a world of difference between the blister and cateract-inducing UV C that kills germs, indeed most life, and the UV-A at that makes your clothes glow at the disco.


    Sorry if the question is incomplete. What I was asking about UV was if used as a sterilizer or I will use it to sterilized my phone or keys is it effective?


    Thank you for your reply.




     


  • 0
    uv lamps are indeed in v short supply at the moment , i use them in my koi pond and change them every 6 months  , they make the bacteria in the water die and clump together forming long strings of what can only be described as goop , then when spun around the filtration system the media can collect them mess .
  • 0
    123misha:o.

    >>> snip

    Sorry if the question is incomplete. What I was asking about UV was if used as a sterilizer or I will use it to sterilized my phone or keys is it effective?


    Thank you for your reply.




     




    The correct wavelength of UV  could be very effective. To kill germs you need UV-C, ( 100–280 nm wavelength, and also the dangerous one to humans as well as to bacteria)

    You would need however to arrange things so that all sides of the keys phone or what have you are exposed more or less equally, understand that any bugs in gaps and cracks that are shadowed from the direct light will not  get killed.

    You must ensure that there are interlocks on the enclosure so that when the UV lights are on you cannot get any part of you near it. The dose for killing bacteria is quite a bit higher  than that which causes skin burns and eye damage.

    A total dose of about 20millijoules per square cm at a wavelength of 260nm should do it in terms of killing most bacteria>99.9%. (The time/ intensity product can be traded, so a weak source for longer.) Longer and shorter wavelengths are slightly less effective.



    Do not use this technique with plastics that bleach and disintegrate  in the sun - they will do the same  in the UV.


    Some background reading
    https://www.sciencedirect.com/science/article/pii/S0305417919300920#bbib0035

    https://iuva.org/resources/covid-19/Woods et al 2015 - UV222 Pilot Study Testing on Volunteers Skin.pdf

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6801766/



     


  • Former Community Member
    0 Former Community Member
    Just to add a bit to Mike's post - I've been looking at a pre publication paper from our Cousins (Boston University) that trialed specifically 254nm at 22mJ/cm2 on SARS-CoV-2 - which had an effective reduction on surface bacteria of 99.99999% exposed for 25 seconds.


    The same wavelength and radiant energy density was effective at inactivating SARS-CoV-2 to a reduction of 99%, in air, when exposed for 6 seconds. The exposure duration is far to long for most air handling plant, so far higher radiant energy density will be needed to be useful in that format, but using UV-C as high level upper room air disinfection in occupied rooms could be quite effective for tackling aerosol virus particles.


    At a room level, however, it's probably far easier to use better ventilation rates - if you achieve that, then using UV-C as well, is a law of diminishing returns.


    For the phone and car keys issue, as Mike says, where the light shines you get disinfection, where it doesn't fall there is no disinfection. You'd be better of washing your hands and wiping the keys and phone in a decent hand sanitizer (or a drop of bleach)


    Regards


    OMS


  • 0
    i watched a program on discovery last week about a robot at gatwick airport that  walks around and emits uv radiation  , totally autonomous and battery driven that goes into each room and works out where best to direct its light to kill the virus , any movement such as cleaners etc it shuts down and moves away, v clever i thought .
  • Former Community Member
    0 Former Community Member
    mapj1:
    123misha:o.

    >>> snip

    Sorry if the question is incomplete. What I was asking about UV was if used as a sterilizer or I will use it to sterilized my phone or keys is it effective?


    Thank you for your reply.




     




    The correct wavelength of UV  could be very effective. To kill germs you need UV-C, ( 100–280 nm wavelength, and also the dangerous one to humans as well as to bacteria)

    You would need however to arrange things so that all sides of the keys phone or what have you are exposed more or less equally, understand that any bugs in gaps and cracks that are shadowed from the direct light will not  get killed.

    You must ensure that there are interlocks on the enclosure so that when the UV lights are on you cannot get any part of you near it. The dose for killing bacteria is quite a bit higher  than that which causes skin burns and eye damage.

    A total dose of about 20millijoules per square cm at a wavelength of 260nm should do it in terms of killing most bacteria>99.9%. (The time/ intensity product can be traded, so a weak source for longer.) Longer and shorter wavelengths are slightly less effective.



    Do not use this technique with plastics that bleach and disintegrate  in the sun - they will do the same  in the UV.


    Some background reading
    https://www.sciencedirect.com/science/article/pii/S0305417919300920#bbib0035

    https://iuva.org/resources/covid-19/Woods et al 2015 - UV222 Pilot Study Testing on Volunteers Skin.pdf

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6801766/


    Thank you so much for your replies. Really appreciate it. So if I have the right amount of UV light then it will be effective right?  Last question though what are your thoughts if I will buy this kind of sterilizer? https://www.getuvpod.com/products/led-uv-sterilizer-box-for-multi-purpose-use-phones-nail-beauty-salon-makeup-sanitizer


    I'm thinking to buy this type of sterilizer since it's cheap and I've seen videos in youtube using this kind of sterilizer.




     


  • 0
    LEDs that emit UV-C are relatively expensive. Be careful - there are lots of products out there that claim to use UV-C LEDs but which have just ordinary or UVC-B/-A LEDs emitting a blue or purple light. Real UV-C LEDs usually have a transparent quartz cover rather than a plastic lens.
  • 0
    I'd be a bit worried that despite having a 'certification' tab on the website, the certificates themselves are not legible - I strongly suspect it only says it complies with the low voltage directive for  mains apparatus ,rather than any specific level of sterilization, or it would  be a bigger clearer image.   I''m naturally suspicious of too good to be true claims. Your mileage may vary as they say.


    Also note one review near the top " Looks really nice. However, the plastic material that came with it that’s supposed to turn into another colour after the sterilization, didn’t change colours at all. So I don’t know if the UV isn’t working or it’s just a defective material "


    That said, low power UV-C LEDs are now reasonably low cost

     2.5mW of optical power for £2.50 per LED  

    though more power  is more pricey

      about 30mW optical power for £15 per LED. 


    I cannot see there being much  more in the box than a microswitch  a low voltage (maybe  5V or 12V) supply and a series resistor or two to set currents, and a $5 microcontroller to set the alarms and so on, so it may well be genuine.




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