Mold, Pest, and Water Damage Response

The following page provides information to help discern if an item has been infested with mold or not.

What is mold?

Mold is a type of fungus which is a simple-celled microorganism that feeds on living organisms as well as dead organic materials, such as those found in libraries. According to the National Park Service there are around 1.5 million mold species.

What causes mold?

The predominant cause of mold is excess water. Excess water can come from liquid water, as a result of leaks, or water vapor, as a result of high relative humidity due to improper storage, faulty humidifiers, or HVAC malfunctions. While most research shows that fungal growth is most prevalent in conditions in which relative humidity is above 60%, humidity levels below this threshold alone will not prevent mold growth, given the fact that favorable germination environments vary from species to species, and therefore libraries should always be on the lookout for mold growth in their collections.

What does mold do?

Mold can have detrimental effects on materials ranging from discoloration and deterioration to further spread of infestation. Even a small mold growth can turn into a large infestation of not properly dealt with in a timely fashion.

How can mold be identified?

Molds come in various colors and sizes, but most molds encountered in a library environment have a characteristic musty odor and active mold has distinct three-dimensional texture and fuzzy appearance. One can differentiate mold from dirt or foxing by these characteristics. However, always err on the side of caution and bring questionable materials to Preservation for further review.

What to do if mold growth is found?

If you notice mold growth, quarantine the material in a bag and bring the item to Preservation in Room 44 of the Main Library. The item is then assessed and sent to Conservation for appropriate treatment, in most cases this means vacuuming the item or irradiation to eradicate the spores. Be sure minimize contact with the mold, as contact may cause further spread of the infestation. Wash any exposed skin that has come into contact with the moldy material and examine the area the item was located for any other moldy items. If there is evidence of an outbreak please inform Preservation staff.

How can mold be prevented?

The best method of mold prevention is a robust environmental monitoring program in tandem with regular cleaning of shelving stacks to ensure proper conditions for collections. The National Park Service recommends that RH levels should always be kept below 65%. If RH exceeds this level please contact Preservation for a portable dehumidifier and further assistance.

Further Reading

Florian, M. E. (2004). Fungal facts: Solving fungal problems in heritage collections. London, UK: Archetype Publications.

—-. (1997). Heritage eaters: Insects & fungi in heritage collections. London, UK: James & James.

National Park Service. (2007, August). Mold: Prevention Of Growth In Museum Collections. Conserve O Gram. Retrieved December 12, 2012, from

Some examples of moldy material:

Magnified image of mold.
Note the three-dimensional texture which is characteristic of active mold growth.
Image of moldy book page.
The mold seen here is characteristic as it displays a variation in color and shape. There are also tide lines which point to previous water damage that incubated mold growth.
Image of a book cover with mold developed under the plastic.
This instance of mold has developed under the plastic book cover. Again, the mold has a characteristic shape and color, despite not being easily identifiable or three-dimensional upon first glance.


Some examples of non-moldy materials which may appear moldy:

Top view of book with dark markings indicative of cockroach infestation.
Insect damage: Staining such as this is caused by cockroach feces rather than mold infestation; this is discernible by noting that the staining is not textured.


Image of orange-red splotches on paper, called "foxing".
Foxing: These red, rust-colored spots are the result of imperfections in the paper making process rather than an active mold infestation. Foxing does not affect the physical integrity of the paper.