Brief description of treatment
What collections materials can be treated this way?
Almost all collections can be treated with nitrogen or argon. Exceptions include:
- One study showed that minerals such as litharge (PbO), cinnabar (HgS), and sienna (mostly Fe2O3) do experience color change in the absence of oxygen (Arney, Jacobs, and Newman 1979), so care must be taken if this is a concern with artifacts or pigments. Prussian blue and ultramarine initially change, but the color comes back. Changes are not noted when pigments are in mixtures, e.g., in paint films. Textiles may be the most likely to change (temporarily).
- Wet artifacts have the potential to reduce the effectiveness of treatment due to insect adaptation to use anaerobic respiration, although this is generally unlikely for the types of pests typically encountered for museum and library pests (Selwitz 1998).
- Load the chamber so artifacts cannot crush each other, accidentally shift, or be crushed by the walls of a soft chamber.
- Seal the chamber (heat-seal for soft wall chambers, zipping shut for retrofitted fumigation soft wall chambers, and closing the door on a hard wall chamber ensuring the gasketry is in good alignment and condition).
- Purge ambient air and oxygen from the chamber. Sometimes this is a two-step procedure; first, introduction of nitrogen to push out the oxygen, followed by the secondary anoxia gas like argon or nitrogen. However, in larger chambers, this additional step has not proven to be necessary since many larger chambers have constant positive pressure to maintain low oxygen levels.
- Monitor and maintain constant gas flow for the duration of the treatment. Treatment duration depends on gas type and species of insect if known.
- Evacuate the anoxic gas from the chamber and return ambient air, while observing proper safety protocols to maintain safe levels for humans.
- Examine artifacts followed by removal of dead insect debris by low suction HEPA vacuuming or using tweezers.
- No chemical residue on artifacts.
- Appropriate for a wide variety of collection materials.
- Argon gas has the additional benefit of preventing bio-deterioration by microorganisms like fungi and bacteria (Valentín 1990).
- More time-efficient than CO2 gas.
- The EPA does not currently list argon and nitrogen as a registered pesticide, so users must research and follow state guidelines for the determinations and requirements for defining what gases are pesticides and if applicator licenses are necessary. This is based on the applicator’s residency and the entity that needs to perform the treatment. For the most up to date information, refer to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) on http://www.epa.gov/pesticides/regulating/index.htm
- Generally, treatment with argon or nitrogen gas is more costly than treatment with CO2 gas, depending on regional rates for gas acquisition
- Nitrogen can in some cases contribute to growth of microorganisms with nitrogenase enzymes that help fix nitrogen as a fuel source. More research is needed in this area to clarify this potential issue.
- Typically steel shell chambers or rooms hard-wired into building electrical and HVAC systems, and become a permanent fixture of the internal building.
- Chambers usually use nitrogen or CO2.
- Include a sealable door in which shelves or carts of infested materials can be inserted. Doors should be secured.
- Preservation Equipment: http://preservationequipment.com
- Constructed of a vapor impermeable film (also referred to as a barrier film) that is heat set together at the seams.
- Very large soft-walled chambers may have an internal frame support of wood or PVC piping to prevent collapse on the artifact(s).
- Can be made to any specific size or shape in-situ, which is helpful for odd-shaped or large objects.
- Reusable soft wall chambers are usually chambers previously manufactured for chemical fumigation techniques that are no longer used or permitted by law (such as methyl bromide) and retrofitted for other gases like nitrogen, argon or CO2. Use an external gas supply.
- 8’ x 8’ x 14’ Trailer chamber with trailer door that can be secured and sealed airtight.
- Both a generator and capacity for a building power source connection
- Electrical, temperature and relative humidity monitoring
- Loading ramp
- Auto-injection and recycle of Argon gas
- Maintain 0.1 – 0.5% O2 level
- External monitoring panels
- Barrier films for chambers (available from several vendors, search internet for the following products):
- Aclar, Marvelseal, and Escal are available from numerous preservation and commercial vendors.
- Heat sealers for vapor barrier film (available from several vendors, search internet for the following products):
- constant heat hand sealers
- Futura Cello Model Sealer, 6″ long, top and bottom heated hand sealer with 3 temperature settings.
- Heat spatulas
- 21st Century Tacking Iron
- Coverite Trim Sealing Iron
- constant heat hand sealers
Burke, J. 1996. Anoxic Microenvironments: a simple guide, Society for the Preservation of Natural History Collections (SPNHC) leaflet 1(1): 1-4. Available from www.spnhc.org.
Daniel, V., Hanlon, G., and S. Maekawa, 1993. Eradication of Insect Pests in Museums Using Nitrogen. WAAC Newsletter 15(3):15-19. Western Association for Art Conservation.
Gilberg, Mark, 1991,The Effects of Low Oxygen Atmospheres on Museum Pests, Studies in Conservation (36):93-98.
Hanlon, G. Daniel, V. & Ravenel, N. “Dynamic System for Nitrogen Anoxia of Large Museum Objects: A Pest Eradication Case Study”, Proceedings of the Second International Conference on Biodeterioration of Cultural Property, Oct 5-8, 1992, Yokohama, Japan.
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Koestler, R.J., C. Tavzes, and F. Pohleven, 2004, A New Approach on the Conservation of Wooden Heritage, International Research Group on Wood Preservation, Paper prepared for the 35th Annual Meeting, Ljubljana, Slovenia, 6-10 June, 2004, available through IRG Secretariat, Stockholm, Sweden.
Koestler, R.J., Parreira, E, Santoro, E.D., and Noble, P., 1993. Visual effects of selected biocides on easel painting materials. Studies in Conservation, 38, 265-273.
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Met Objectives. 2002. “Biodeterioration in Museum Collections” Sherman Fairchild Center for Objects Conservation. Metropolitan Museum of Art. 3(2).
Selwitz, C. and S. Maekawa 1998. Inert Gases in the Control of Museum Insect Pests. Los Angeles: The Getty Conservation Institute. http://www.getty.edu/conservation/publications/pdf_publications/inertgases.pdf
Valentín, N. 1990. Insect eradication in museums and archives by oxygen replacement, a pilot project. ICOM Committee for Conservation 9th Triennial Meeting, Dresden, German Democratic Republic, 26-31 August 1990, Preprints, vol. 2, ed. K. Grimstad. Los Angeles: ICOM Committee for Conservation. 821-23.
Valentín, N. 1993. Comparative analysis of insect control by nitrogen, argon, and carbon dioxide in museum, archive, and herbarium collections. International Biodeterioration and Biodegradation 32:263-78.