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From:  gwyee@r...
gwyee@r...
Date:  Thu Nov 9, 2000  1:56 am
Subject:  Re: [vocalist-temporary] MISC: "germ-free" humidifiers


At 03:50 PM 11/8/00 -0500, you wrote:
>I've seen advertised a germ-free humidifier which, "uses ultraviolet light
>to kill 99.99% of the germs and mold spores in the warm vapor it fans into
>household air." Does anyone have experience with this type of humidifier?
>Would there be an appreciable difference between this and the regular
>ultrasonic humidifiers? (I do in fact have a mold allergy, which is why
>I'm considering this type of thing.)

Dear Naomi,

My two cents: The germicidal activity of UV irradiation is through its
induction of dimeric cross-links in thymidine (as I recall) residues of DNA.
It takes at least 15-20 minutes of direct and close exposure for a standard
UV sterilization lamp to kill bacteria. The cross-links prevent them from
multiplying. Spores (fungal or bacterial) are much more resistent. So UV
light exposure to the "steam" floating past it will do little to nothing.
They are also omnipresent so the small amount which may be present in fresh
water poured into your humidifier would be relatively insignificant. If you
want to reduce their presence even more, boil the water for 10 mins. or use
a humidifier that generates steam by boiling the water inside it. If you
are concerned about spores in the atmosphere of your home, install an
electrostatic air filter system (what my parents did for me, their asthmatic
child). Water left stagnant in a humidifier can team with germs, however.
But regardless of the humidifier, the remedy for this is to not let the
water stagnate. Bottom line-use a humidifier that boils the water and
change the water frequently. It's a lot cheaper and more effective.

GWendel [MD, MSc (genetics-molecular biology), PhD (genetics), etc...]
and erswhile tenor


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