humidity control

[Sally Shelton]

Stuart: a lot of older published figures may be voodoo numbers (there was
a major meeting on this last year), but one number is truly critical.
Keep the relative humidity well below 70%, as that seems to be the
threshold level for lots of exuberant microbial activity. Temperature is
most important in relation to RH levels, though extremes and fluctuations
are no good.


In general, collections appreciate being kept cool, dry, and in the dark,
though people may not. It would be better not to have the work area in
the main collections storage area for just this reason, as well as others
(exposure to light, UV, food, drink, pests...). However, good cases with
good gaskets with provide a level of isolation for the specimens. Bear in
mind that cooler temperatures slow some fornms of pest activity as well
as adverse environmental reactions. Keep the specimens in the cases at
all times when they are not in use: no case can protect a specimen out in
the open. Light and UV damage is cumulative and irreversible.=20


Our temperature levels for fluid-preserved collections in our expanded
building are being determined in large part by fire codes and will be
quite low (15-16<smaller>o</smaller> C). The work area will be out of the
collections range and separately controlled. In general, a temperature
range of 20<smaller>o</smaller> C <underline>+</underline>
5<smaller>o</smaller> C, and a relative humidity range of 50%
<underline>+</underline> 8%, should be optimal for most of the
collections you describe. The steadier this is, the better. If you have
sensitive material which needs more stringent RH control below this
range, it's better to construct inexpensive microenvironments with
conditioned silica gel or saturated salts than it is to try to use
expensive building climate systems to reach that kind of pinpoint level.
Contact me off-list for more information on this: you can't just throw
silica gel into a case and walk away. There are also designs for more
elaborate active systems for internal climate control of storage and
display cases.=20


The microenvironment approach, specifically the use of anoxic enclosures,
is also strongly advised for pest control as a very safe and useful
alternative to fumigation.=20


Oh, yes: DON'T guess. Buy a good recording hygrothermograph or two as
well as some spot-check hygrometers, and check the room levels weekly for
at least 18 months before you fully sign off on the building control
system. Do not depend on human comfort as any kind of useful guide to
environmental levels. It doesn't work. People aren't meters. The
hygrothermograph charts will give you concrete evidence for the building
engineer on the days when his remote computer says that everything is
fine and you are boiling or freezing and the collections are covered with
kudzu. You'll have to calibrate the hygrothermographs periodically, but
that's easy. Again, I can give you details off-list.


Cheers, Sally=20





At 10:18 AM 1/13/98 -0500, Stuart Fullerton wrote:

>Now that the Bug  Closet has expanded and all the university mammal,

>herptile, ornithological,  ichthology and arthropod collections are

>under one roof and in one open range, along with a revitalized fume
hood,

>emergency shower, and work benches, they have refurbished the air

>handeling system. Complete with heat, cooling, and a humidistat to=20
help

>control the humidity.  Does anyone have any suggestions as to a most

>probable temperature and humidity setting suggestion  for the

>collections , keeping in mind the need for some human comfort for

>assortedf volunteer-student help?  Note: the botanicals are kept
elsewhere

>in another building.

>

>Thank you very much.

>

>cheers!!!!  rof

>

>Stuart M Fullerton ROF, Research Associate in charge of Arthropod

>Collections (UCFC), Biology Dept. University of Central Florida,
Orlando,

>Florida, 32816, USA. stuartf at pegasus.cc.ucf.edu

>




____________________________________________________________________________=
_____


<center><bold>Sally Y. Shelton

</bold><smaller>Director, Collections Care and Conservation

President-Elect, Society for the Preservation of Natural History
Collections

San Diego Natural History Museum, P. O. Box 1390

San Diego, CA   92112

phone (619) 232-3821, x226; FAX (619) 232-0248; <<sshelton at sdnhm.org>

<<http://www.sdnhm.org>

</smaller></center>