Yes, that "musty" smell is the smell of trouble, spelled M-O-L-D.
And, yes, it can spread, so you need to get on top of the problem before
it gets out of hand.

I qualify as a "mold-fighter" on the basis of an on-going "bloom"
attacking our older bound periodicals stored under poor environmental
control.  I recommend you get "Mold" (Conservation Center for Art and
HIstoric Artifacts.  Technical Series No. 1, 1994) available from the
Center at 254 South 23rd St. Philadelphia, PA, 19103 (address from piece).
Much of the published material deals with disaster recovery and the
prevention of mold, which is a different problem from the on-going
problems caused by general environmental deficiencies.

Also, if the problem proves to be a major one, be sure that all the
players are involved.  We have found our custodial and cleaning staff to
be invaluable allies, once we showed them the potential sources of
trouble, e.g., dust, and taught them how to recognize problems, for
example, by the characteristic order.

Carol Schaafsma
Head, Collection Services Division
University of Hawaii Libraries

carols@hawaii.edu
Phone: 808-956-2473
FAX:   808-956-5968