Bugs, books, and ice cream freezers

June 17, 2020
Annie Matthys
Library materials bagged and isolated, undergoing observation for potential pest activity.

Within the last few months, being in quarantine has become something we feel all too familiar with; and, perhaps, this is the first time a majority of us have added the term and concept to our daily lives and experience. For those of us in preventive preservation, however, quarantine is actually a facet of our duties, as we quarantine library and archive materials as a means to safeguard collections.

Why quarantine collection materials?

Materials need to be quarantined to contain a problem - typically insects or mold - and prevent it from becoming more widespread, potentially infecting materials in shared spaces or containers. Quarantine, and the treatments materials undergo while in this phase, will stabilize them and prepare them to safely return to their home locations.

Symptoms: When do collection materials need to be quarantined?

Materials that need to be considered for quarantine will exhibit some - or all - of the following:

Potential insect activity:

  • Someone sighted a live or dead insect inside a book, for example, or within collection materials, such as in an archival box

  • There is other visible evidence of insect activity, such as webbing, wings or other parts, casings, etc.

  • Newly acquired materials have visible damage (holes, grazing marks, etc.) caused by insects feeding on their surfaces 

  • There are visible droppings, which we call “frass,” inside materials, around them on shelving units, or inside storage boxes

Potential mold issues:

  • Someone notices what they suspect is active mold on materials, which will appear more slimy and fuzzy or hair-like

  • Someone notices what they suspect is inactive mold, which is dry and powdery

  • A strong mildew smell emanates from materials

These “symptoms” can be observed by any library staff, who can immediately bag the item in-place and isolate it from the collection until completing the materials quarantine form that will alert the Preservation Department to the issue and prepare them for a thorough inspection upon its arrival into the Quarantine Room.

Diagnosis: Who inspects isolated materials?

The bagged materials will be sent to our Conservation Lab, where they will then be placed, with identifying paperwork, in the Quarantine Room to await inspection by Preservation Department staff. When “diagnosing” the problem, it is important for Preservation staff to take the proper precautions for their health and safety, including the use of personal protective equipment (PPE), because the materials could spread mold spores and/or contain potentially harmful biological materials left behind by insects and rodents.

First, Preservation staff will visually inspect the materials and review the submitted materials quarantine form. If there is evidence of insect activity, the materials will undergo up to 1-2 weeks of isolation and observation in order to capture and identify the insect species. With suspected mold, it must be determined if the mold is active or inactive.

Preservation staff must thoroughly insepct items for evidence of pest activity and mold.


Treatment options are dependent upon many factors and require careful consideration and consultation between Preservation staff.

Insect Activity

Generally speaking, treatment methods for materials with active insect issues will be based upon the insect species identified. In most cases, insects can be eradicated by exposure to -30° C (-22° F) for a minimum 72 hours, but ideally for 7 days. To achieve these temperatures, we use a commercial-grade ice cream hardening freezer. However, if the species is particularly hardy and/or freeze-resistant, freezer treatment may be one facet of the process or eliminated as an option altogether.

Alternately, for those more hardy species alluded to, the creation of an anoxic microenvironment is used to treat materials. If you are curious to know what an anoxic microenvironment is, museumpests.net (one of our favorite resources) provides an excellent explanation:

“By depleting atmospheric oxygen to very low levels using reactive oxygen scavengers within an impermeable enclosure, a modified atmosphere composed almost entirely of nitrogen can be created.  All developmental stages of insect pests can be eradicated if atmospheric oxygen levels within such an enclosure are maintained below 0.5%....”

The creation of this “impermeable enclosure” requires not only special materials but also a considerable amount of skill and practice: if not executed correctly, the microenvironment can fail and will need to be re-created. The materials will remain in this enclosure for 21 days.

Mold Issues

As for mold, if it is determined to be inactive, careful cleaning in the Conservation Lab will be necessary, utilizing equipment that will ensure mold spores are not exhausted back into the air but also that the structure of fragile materials is not compromised.

Active mold must be addressed quickly by being placed in the freezer for at least 4 days at -20 °C (-4°F) to stop growth and prevent new growth (this is “deactivation,” or making the mold go dormant). Once “deactivated,” Conservation Lab staff can clean the materials.

Release from quarantine

Once materials have undergone treatment, Preservation staff will prepare for them to leave the Quarantine Room - but in a very measured, cautious way. For those materials that underwent treatment for insect eradication, another period of isolation and observation (up to 1 month) is necessary to ensure treatment was successful and it is insect-free before being returned to its home location.

Materials that received cleaning after mold deactivation are ready to be released from the quarantine workflow - and back into an environment with a stable temperature and relative humidity - as well.

Post-treatment, library materials must be isolated and bagged again while Preservation staff monitors for insect activity.

Why this process is important

As you can see, the process is not simple, especially when you consider that this is the condensed outline of procedures! Materials quarantine takes time; expertise; a strict adherence to procedures and guidelines to be successful; detailed documentation; careful consideration; and collaboration among colleagues. However, the process is critical because it allows for immediate action to be taken to keep the largest number of collection materials safe from potential damage, all the while retaining the materials on-campus and in a workflow carefully overseen by Stanford Libraries staff.


Annie Matthys

Annie Matthys

Preservation Specialist