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UV-C for mold erradication

  1. Sep 2, 2007 #1
    I will be doing some research soon using UV-C as an alternative to biocides for mold erradication.

    I have a few potential problems with this:

    One is, I know that UV-C is strong ionizing radiation, but I am concerned about it's ability to penetrate the surface of the affected material (mainly wood) as I know that many materials easily block UV.

    How deep would mold growth extend below the surface of the wood on a freshly affected area?
    Would the UV-C be able to penetrate deeply enough to thoroughly irradicate it if it did?

    I know that biocides are effective because they soak into the wood when applied as liquid.

    Just that some people usually don't like all those nasty chemicals in their homes.

  2. jcsd
  3. Sep 2, 2007 #2

    jim mcnamara

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    What species of mold are you going to test?
  4. Sep 2, 2007 #3
    S. chartarum or S. cylindrosporum ( don't know if the spelling is correct), but I believe these are the main molds that grow on wood products after they have been exposed to miosture and are left in dark unventilated areas.

  5. Sep 3, 2007 #4


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    Here is a start, but I recommend finding other sources as well.
    See - Subtypes

    UV is used in hospitals, but that may be UV-B. I have seen UV system in areas where immuno-compromised patients are present.

    UV-C is more penetrating than UV-B, which is more penetrating than UV-A. X-rays are more penetrating than UV-C, and gamma-rays are generally more penetrating than X-rays, but it is really a matter of energy. The high the energy/frequency, the greater the penetration.
  6. Sep 3, 2007 #5


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    These seem like they should be questions addressed by your research, especially the second one if this is a novel application of UV-C.

    For your first question, what do you mean by "freshly affected?" If you're killing the organisms as they land on the wood, as a preventative treatment, then they won't have had time to penetrate at all. But, is this really your intention, or a practical application? If someone is attempting to eradicate mold, presumably it has grown to the point of being noticeable and has likely been present for a while before discovery. It may be better to find out what the maximum depth of penetration is...can it fully penetrate wood, or is it always limited to a certain depth from the surface? This will probably require either surveying sites with mold or growing some mold in the lab on wood that you can then cross section and look for depth of penetration. It would also be helpful to get some input from perhaps the engineers here on how deep penetration of a mold would be before treating it isn't an option anyway...i.e., when the wood is too badly damaged and weakened to remain structurally sound even if you killed all the mold currently on it.

    For the second question, it seems that is best answered empirically. If you have your UV source and your blocks of moldy wood, you can determine what intensity of UV, what duration of exposure, etc., is required for killing the mold, to what depth, and how complete it would be.

    Another consideration...IF this treatment effectively kills surface molds, and is safe to use near workers, rather than treating wood already damaged by mold, it may be more useful at the entrances of a room or on unaffected walls following removal of affected wood in order to prevent any mold spores from spreading and initiating new colonies as damaged wood is removed. Would it kill spores, or just the adult organism?
  7. Sep 3, 2007 #6
    This is not a novel application of UV-C for mold irradication. It was used at one time, but for some reason it was not the preferred method of treatment.

    I do know that UV-C does kill organisms like mold, and the clients that I encounter from time to time, that are sensitive to mold are also the ones that are sensitive to chemicals.

    There would be no exposure of UV-C to the client as molds grow in damp, dark areas with poor ventilation. And if not then those ereas would be off-limits. The UV-C bulb that I have will burn the cornea of your eye in about 30secs. Very similar to flash burn from arc welding, but I don't think the wavelength of that UV-C is as short.

    I'm just looking for a green alternative to the standard chemical treatment of mold.
    Not looking for maintenence, more of primary intervention when it actually is detected.

    There has been some systems developed for UV-C use in ventilation systems, but this didn't last long as the bulbs that were costly to replace didn't last long. Maybe that's why it never became popular in any situation.

    Looks like it's time to do my own research on this subject, like you said moonbear get some moldy blocks of wood and the UV-C bulb and make a setup. Just have to get my micrscope back from my daughter.

    Thanx all, I eppreciate your input.

    BTW astronuc I was considering x-rays, a little too radical though.

  8. Jul 24, 2010 #7
    Did anybody get around to doing any of those experiments? I have some mold on a table I want to remove, but it looks like it has penetrated the wood at least 0.5mm or so. I need to know if goes down more than a couple mm's and how far down the non-visible mold goes.

    While I'm at it, I might as well ask if any of you know of all wood stains protect from mold.
  9. Jul 24, 2010 #8
    This seems like a bad choice for mold removal from a table compared to chemical methods. In the case of the OP, it sounds like chemical methods are not viable based on his clientele, but for you that is presumably not an issue?
  10. Jul 25, 2010 #9
    All the medical germicidal lamps I ever have heard of have used UVC. I cannot answer for OTC toys and traps for the laity.

    Astro, I really cannot accept this as it stands. Penetration through various media by light depends on the regime and how photons of various frequencies interact with the media in question, not primarily the energies (which are of course a strict function of frequency). X- and gamma rays penetrate more deeply because they interact differently with orbital electrons. UV and visible light mainly interact with the electrons, and UVC most strongly compared to UVA and UVB. As a result it penetrates less deeply and does more damage where it does penetrate. (By way of rather tenuous comparison, UVC hardly reaches below the stratosphere, just enough UVB reaches sea level to sunburn silly tanners, and quite a lot of UVA gets through.)

    As for the effectiveness of germicidal lamps under the conditions required, they certainly are generally effective and low-pollutant, except for producing a bit of ozone. I assume that it would not be practical to carry out tests for this requirement, so I would enquire from the supplier whether the lamps are recommended for the purpose. Certainly the treatment is superficial, but so are many valuable germicidal treatments. If the user keeps the place clean and cannot directly look at the lamp when it is on, it should be OK in general. If dirt can accumulate in corners and cracks, all bets are off.

    I would not expect UVC to penetrate 1mm of solid wood, especially if it is wet. If the wood is solid and dense, I would not expect relevant fungi to penetrate deeply.

    Beware if the lamp directly illuminates materials like butter and anything else that is to be eaten or smelt. short wave UV can make fats go violently rancid and destroy vitamins.

    Hmmm. If the lamp is to be waved over the table by a layman to de-germ it on a whim, you might as well use a magic wand.

    If you decide against UV (which certainly is an economical broad-spectrum microbicide) then safe, odour-free options include metal salts such as zinc, ( and copper, as long as there will be no contact with reactive metals such as iron and aluminum) or peroxides. Zinc and copper salts in concentrations adequate to control superficial fungi would be more like human nutrients than poisons.

    Good luck,

    Last edited: Jul 25, 2010
  11. Jul 25, 2010 #10
    Regarding the portion in bold, am I the only one who's used that very fact as the basis for a couple of truly horrendous pranks? :biggrin:
  12. Jul 25, 2010 #11
    The only one I've heard of!:bugeye:

    Dare I ask?

  13. Jul 25, 2010 #12
    Hmmm, lets just say that in retaliation for someone dropping HCL on my neck, then slapping baking soda on, I turned their margarine into something truly foul. This is all in the context of people pissing blue, skittering slivers of sodium in water... you know, good times. :wink:

    Sometimes I think it's a wonder that we ever survived high school and early college. :rolleyes:
  14. Jul 25, 2010 #13
    Good grief! Just as well I would never dream of anything of the kind! o:)

    Naturally! :blushing:
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