This is a valuable breakdown of RH issues.
One question for Randye: I notice you're in Iowa. Consequently, and
as Charlie mentions,
you likely see RH fluctuations from season to season. I agree that
20-30% RH is great for
the storage of AV media and playback equipment but, if your RH jumps
to 75-80% in the
summertime - which is entirely possible in the Midwest - you're
really giving your AV holdings
I often make an allusion in these cases to musical instruments,
especially stringed instruments:
You know how they can go in and out of tune when taken from the house
into the cold and then
back into another building? The same expansion and contraction
affects AV media as well,
something that will compromise their stability over time. (Nitrate
layers on lacquer discs, for example.)
So fluctuations in RH are equally important to monitor and keep under
control. And in this case,
i might actually argue that an RH closer to 40-50% makes sense in the
winter if (**and only if**)
your summer RH levels are in the neighborhood of 70-80%.
At least it would ease the whiplash caused by radical (20% --> 70% --
> 20% etc) RH fluctuations.
Archivist for Recorded Sound Collections
Hoover Institution Archives
Stanford, CA 94305-6010
email: [log in to unmask]
On Dec 4, 2008, at 10:16 AM, Charles A. Richardson wrote:
> Hi Randye:
> Humidity levels are relative to temperature. You did not indicate
> the temperatures involved. The thing to do is have good
> instruments to watch and measure both temperature and humidity
> readings periodically. You will notice major changes with the four
> seasons of the year and also perhaps with the number of people in
> the room.
> The low humidity is good for both media and equipment as it retards
> various negative unwanted chemical reactions and also keeps down
> the risk of the growth of mold and fungus. Humidity of 20% to 30%
> is excellent for media and is typically recommended in various well
> established long term storage standards for many chemical reasons.
> Your note did not mention heating and air conditioning issues. Air
> Conditioning dehumidifies and removes moisture when it drops the
> air temperature. Heating is of different kinds. If the heating is
> by radiators, or electric coil heaters, these tend to dry out the
> air and drop the humidity. Heating by forced air systems may or
> may not have a humidifier in the furnace room which can be adjusted
> to add humidity moisture as desired and specified to the warm air
> circulated through the system. As I do not know any of these
> heating and cooling issues in detail, I simply make the above
> general comments.
> Evidently the staff or others are feeling some discomfort at the
> lower humidity levels, with perhaps dry throats, etc.
> If the humidity is raised for people, then this is not good for the
> media and equipment, so there is a bit of a conflict on the
> humidity issue. The best thing is to leave the room humidity as it
> is, not add a humidifier, and for those who feel dried out to drink
> some water, soft drinks, etc. occasionally to re-hydrate
> themselves. Most places have humidity levels that are way too
> high and thus have lots of high humidity related media and
> equipment problems. They have to use dehumidifiers to get rid of
> the high moisture. So consider yourself fortunate not to have the
> high humidity problem. If people will drink more water based
> liquids, then everyone and everything should be happy.
> Also another issue not mentioned that may be a factor in staff
> discomfort is Oxygen levels and Carbon Dioxide levels. If the
> room is tightly sealed and does not get fresh air circulation
> occasionally, and there are a lot of people in the room, they can
> consume a fair amount of Oxygen, just from ordinary breathing. The
> Carbon Dioxide levels will also then go up, and this can make
> people feel stuffy, drowsy, or uncomfortable. It might be a good
> thing to look into the fresh air and Oxygen level issue just to be
> sure things are OK on this front, especially when a lot of people
> have been in the room for a long time. Are doors closed or open?
> Hope this helps. Charlie Richardson
> On Dec 4, 2008, at 11:39 AM, Jones, Randye wrote:
>> Good day, all!
>> We are considering installing a humidifier to address the low
>> humidity (21-22% at present) in our library's Listening Room.
>> However, I'm very concerned about whether it would adversely
>> affect the audio and video equipment and/or the video and audio
>> collections housed here.
>> One thing we are considering is placing the humidifier in the
>> outer public area so that the steam generated would be less likely
>> to directly contact the equipment or collections.
>> What is your experience? It has been suggested that the higher
>> humidity would not only benefit the staff but the materials in the
>> Thanks for any input you can provide.
>> | | Randye Jones
>> | ) | Listening Room Supervisor
>> / | | Grinnell College Libraries, Grinnell, IA 50112
>> ( | ) | [log in to unmask]
>> | | Phone: 641-269-3365 FAX: 641-269-4283