On Wed, 27 Feb 2013 10:31:08 -0700, chaniarts
wrote:

the usual culprits are ozone or uv rays.

You can eliminate UV from the guess list. I've had it happen in a
closed toolbox, where no light enters except perhaps twice a year.
It's also happening in my steel drawer tool boxes, where again little
light enters. Ozone is a possibility, but I don't have any obvious
sources for excessive ozone in the shop (Hi-V, electrostatic
precipitators, negative ion generators, laser printers, etc). However,
I do store aromatic chemicals nearby, which may be the problem.

Also, an important clue is that I can have a drawer full of plastic
handle hex spintite wrenches, and only some of them will have a "mold"
problem. This implies that the culprit is resident mostly in the
plastic and not the environment.

Opinions seem to vary...

Mold growth on plastic:
http://www.ehow.com/info_8526040_fast-mold-grow-plastic.html

Can mold grow on plastic and, if so, is there a way to clean it? - See
more at:
http://moldblogger.com/can-mold-grow-on-plastic-and-if-so-is-there-a-way-to-clean-it/

How to Remove Mold From Plastic:
http://www.ehow.com/how_7939800_remove-mold-plastic.html

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558