Author Topic: Home Made Germicidal Lamps  (Read 218 times)
merc
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Home Made Germicidal Lamps « on: March 25, 2020, 01:16:35 PM » Author: merc
While I believe I'm not overconcerned about the current "plague", these days I find quite useful disinfecting our entrance hall (dirty hand touched handles + wrapped things brought from a supermarket) a bit.
As discussed with another LG member via PMs, we came to the same conclusion - to prepare a "germicidal" lamp from a spare 125W MV lamp. (I've got several of them.)

That lamp made last week and already used several times looks exactly the same like this one - made 6 years ago(!) - it's been extracted from the same uninteresting Polish Helios branded Chinese MV lamp.
It definitely produces ozone but I'm not sure if the UV-C range radiated is really the same as that by true germicidal lamps? Wikipedia suggests it should be so.
What I'm more concerned about is the bare arc tube (burner) exposed to dust, possibly to some insects etc. - while I avoid touching it (the trick known from handling halogen lamps) - shouldn't it be cleaned by pure alcohol from time to time? Or better not?
Thanks for sharing your tips and experience.

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dor123
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Re: Home Made Germicidal Lamps « Reply #1 on: March 26, 2020, 12:58:34 AM » Author: dor123
Modern germicidal lamps don't produce ozone, as they are made from quartz that blocks the vacuum UVC wavelength that produces ozone.
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merc
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Re: Home Made Germicidal Lamps « Reply #2 on: March 26, 2020, 01:13:54 PM » Author: merc
Modern germicidal lamps don't produce ozone, as they are made from quartz that blocks the vacuum UVC wavelength that produces ozone.
That's true.
I believe that breathing relatively low ozone concentrations for a very short time (until you turn off the lamp) should not be a health risk and the thin ozone layer also probably doesn't lower the UV-C effects.
But blocking it makes sense in hospitals (fast disinfecting an operating room just before an operation etc.).
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Ash
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Re: Home Made Germicidal Lamps « Reply #3 on: March 26, 2020, 01:21:33 PM » Author: Ash
I think the outdoors air can be assumed clean (unless there are people breathing right outside the window), so the room can be ventilated at the same time as the lamp is working (not considering whether it is ok to fully open the window due to air temperature)

To prevent any exposure to the lamp itself and to the Ozone, control it from outside the room with an extension cable
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Re: Home Made Germicidal Lamps « Reply #4 on: March 27, 2020, 01:16:16 AM » Author: Medved
As a "quick available something" it will work, but if you have real purpose designed germicidal lamp, it will perform way better.
The thing is, the high pressure surrounding of the arc tends to selfabsorb most of the UV, starting already from UVA. So even a G15T8 will have higher useful output than the 125W HP-MV. Dont get fooled by the extra ozone generation: The purpose made germicidals have very steep cur off filter, so even with higher amount of UVC, they generate less ozone.
And better to underdrive the arc a bit (e.g. operate the 125W lamp on an 80W ballast - lower pressure means less selfabsorbtion, so the UVC remains about the same power, but the lower temperature means it will most likely survive longer exposed to air.

And if you have the possibility to keep out of the room for some good ventilation afterwards, generate and concentrate the ozone there is not bad idea: Unlike the UV alone, it soaks into everything and so disinfect it even on surfaces hidden from the UV. But then you need good ventilation period toget rid of it and make it safe for people again. This is the way, how public transport vehicles are treated these days, byt the generators are purpose build devices for this. Dunno how exactly they work (quite small boxes, with rather low power input, treatment takes few minutes plus ventilation), dhey do not have to use UV, some corona discharge sounds to me more likely.
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merc
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Re: Home Made Germicidal Lamps « Reply #5 on: March 27, 2020, 12:51:58 PM » Author: merc
These seem to be good tips. Thanks for them.
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