In light of the news regarding the insect infestation at the Pannonhalma Library, we will briefly outline how we can protect ourselves against insect infestations and, if the problem has already arisen, how the infestation can be treated, what procedures can be applied, and what tools are needed to implement them successfully.
Organic substances serve as food for pests. This is why they find optimal environmental conditions for their survival in museums, archives, libraries, and their storage facilities. They can enter from the outside through windows and doors, or along with incoming items, via people, or even from within the building itself.
The first step is prevention (e.g., installing mosquito screens on windows, keeping doors and windows closed, maintaining cleanliness, monitoring with sticky traps, reducing humidity and high temperatures, using a quarantine storage area where infestations can be detected before objects enter the collection, etc.).
If an infestation is detected, the infected batch must be immediately isolated, packed, and then the pests responsible for the infestation must be identified. In the case of art objects, it is very important that the methods used for disinfection do not damage the objects and do not pose a danger to people. Not all commercially available substances or equipment are suitable for this task.
There are several known methods for pest control (e.g., freezing, heating, controlled heat treatment, nitrogen treatment, oxygen deprivation), but some of these cannot be applied to all types of materials or objects. The choice of the appropriate treatment always rests with the restorer.
Treatments using an oxygen-free environment (anoxic treatment)
Treatments involving the removal of oxygen can be applied to all objects.
These treatments are based on the fact that for most organisms, including insects, the presence of oxygen in the air is indispensable. Removing oxygen and maintaining an oxygen-free environment over the long term leads to the destruction of harmful insects. This can be most easily achieved in a closed space, either by replacing oxygen with nitrogen or by fixing the oxygen content in the air. These two procedures can be applied to all objects.
Nitrogen treatment is recommended for disinfecting materials in large quantities or with a large surface area. This process takes 4–6 weeks. Oxygen adsorbents can be used to treat smaller quantities and items of smaller dimensions. The treatment duration is also 4–6 weeks in this case.
Treatment process in an oxygen-free environment:
Nitrogen treatment:
The basic principle is to replace oxygen with nitrogen in a closed chamber filled with nitrogen or in a mobile tent made of special foil, which can be hermetically sealed by welding. The nitrogen can come from a nitrogen tank or a nitrogen generator can be used.
The desired oxygen level of 0.3% is reached in the chamber within 4–6 weeks. Due to the insect’s activity, which depends on temperature, the procedure can be performed at temperatures above 20°C. During the procedure, temperature and humidity must be monitored and controlled. The nitrogen generator can be purchased or rented.
Creating an oxygen-free environment using an oxygen absorber:
This is ideal for small items in small quantities that require a lower budget. During treatment, bags or sacks made by welding special airtight film are required, which hermetically seal the items, as this procedure also works only in enclosed spaces. Within 5–6 weeks, the adsorbent binds the oxygen, and the insects die inside the sealed bags. You must ensure that the material of the airtight bag does not deteriorate, as in this case air enters the system and the treatment must be restarted after the defect is repaired.
Oxygen-absorbing capsules for art objects
For this reason, standard PE films available in retail stores cannot be used, as they do not provide an airtight seal; the material itself allows air to pass through and cannot maintain an oxygen-free environment for 4–6 weeks.
For smaller objects (approx. 30x40 cm), factory-sealed bags on three sides are available in various sizes; these must be heat-sealed on one side after inserting the object and the necessary treatment materials.
Absorbents that can also be used for art objects are available in packages suitable for deoxygenating 5 or 250 liters of air. The absorbent cannot be reused and is not considered hazardous waste; therefore, upon completion of the treatment, it can be disposed of in household trash.
Checking the oxygen level
Since the treatment is effective only if the oxygen-free state is maintained for at least 4 weeks after it has been achieved, it is necessary to check the oxygen level in the enclosed space.
The simplest method is to use indicators that clearly signal the presence of oxygen by changing color. Therefore, visibility within the enclosed space must be ensured, and the condition of the indicators must be continuously monitored so that, in the event of any damage or a weld failure, the procedure can be resumed as soon as possible.
Maintaining the temperature required for treatment
In the case of insect infestations, the procedure can only be performed at temperatures above 20 °C, as insect activity decreases at temperatures below 20 °C, and the treatment will thus be ineffective or take excessively long.
Humidity control
The absorbent can heat up to 40 °C during oxygen absorption, which can lead to excessive water vapor formation or changes in humidity. To control this, it is recommended to place dry clay pellets, silica gel, or, if necessary, Prosorb cassettes in the enclosed space.
It should also be noted that heating the absorbent can damage the artwork placed inside, so it must not come into direct contact with it.
Workplace Safety Rules
The nitrogen-rich environment displaces oxygen, which can pose a suffocation hazard to people as well. During work, special care must be taken to ensure that specialists work in an enclosed space with an adequate supply of fresh air.
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Cover photo: Lujza Hevesi-Szabó (Telex)