Relative humidity

Our Libraries is currently making plans to upgrade the environmental
controls for our storage facility.  In trying to determine the ideal
relative humidity, I found several variations among the preservation
literature.  What is the latest recommendation for the relative humidity
for book collections, and for other materials that are usually housed in
library facilities, i.e., microforms, photographs, etc.  Thanks.

Diane Lunde,
Conservation Librarian
Colorado State University Libraries 

                                  ***
                  Conservation DistList Instance 6:28
                 Distributed: Friday, November 20, 1992
                        Message Id: cdl-6-28-005
                                  ***