Controlled atmosphere fumigation is the practice of altering the relative concentrations of the components of air to kill insects. Nitrogen (N2) and argon (Ar) are two of the gasses used in controlled atmospheres which are effective in causing insect death within 2-6 weeks, as shown by measuring insect respiration before and after treatment or examining mortality of insect cultures present in vials. In both N2 and Ar treatments, a significant reduction of oxygen (O2) from atmospheric concentration (21%) is required. There are many studies within agricultural and conservation literature investigating the oxygen concentration effect on insect mortality with a range of conclusions which depend in part on the species, temperature, and material being treated (see bibliography at the bottom of this page). Based on these studies, efficacy improves as O2 levels are reduced from 1% to 0.01%. Oxygen levels above 1% rapidly become less lethal to insects.
In addition to using lower oxygen concentrations, increasing temperature of the treatment helps speed up mortality of insects under controlled atmospheres.
Comparing the two cover gasses for low oxygen fumigation there is evidence that argon is somewhat faster than nitrogen at killing insects (Valentín 1993) however both approaches will result in good control as they work to limit oxygen below the range of concentration that is essential for insect life.
Non-insect targets?
Additionally, argon kills some fungal tissue while nitrogen permits the same fungi to survive anoxia (Koestler, Tavzes, Pohleven 2004).
Mode of action?
The oxygen deprivation causes a disruption in the glucose production within insect bodies, resulting in weight loss and eventual insect death. Controlled atmospheres are not toxic per se, but nitrogen and argon cause malfunction of insect metabolism effectively causing death.
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.
Systems
Modified atmospheres using nitrogen and argon are usually continuous-flow systems with soft or hard walled, vapor impermeable chambers. The continuous flow of gas initially purges the chamber of oxygen, and then maintains low oxygen levels to compensate for leaks.
- 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.
- Suppliers:
- 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.
- Suppliers:
- Maheu & Maheu Pest Management www.maheu-maheu.com
- 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
- Oxygen meter, analyser or indicator.
- Note that there are a variety of products that can be used for monitoring low-oxygen treatments. Some such as the AnoxiBug Alert, a device manufactured by Hanwell for the Anoxibug system or the Mitsubishi Ageless Eye may produce variable or inaccurate results. The 2020 study by Crowther and Breitung on the Evaluation of low detection limits of a range of low-cost oxygen meters for anoxic treatments provides information that may be useful in choosing a meter or analyser.
- constant heat hand sealers
Annis, P.C. Towards rational controlled atmosphere dosage schedules: a review of current knowledge. In: Donahaye, E; Navarro, S (eds.)., editor/s. in: Proceedings 4th International Workshop Conference on Stored-Product Protection; 1986, September; Tel Aviv, Israel. 1987. pp.128-148
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.
Crowther, G and E. Breitung, 2002. Evaluation of low detection limits of a range of low-cost oxygen meters for anoxic treatments.
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.
Koestler, R.J., 1992. Practical application of nitrogen and argon fumigation procedures for insect control in museum objects. Toishi, K., Arai, H., Kenjo, T., Yamano, K. (eds.) 2nd International Conference on Biodeterioration of Cultural Property, Yokohama, Japan, 5-8 Oct 1992, preprints pp 94-96.
Koestler, R.J., 1993. Insect eradication using controlled atmospheres, and FTIR measurement for insect activity. ICOM 10th Triennial Meeting, Washington, D.C. Vol. II, 882-886.Koestler, R.J., 1996. Anoxic treatment for insect control in panel paintings and frames with argon gas. American Institute of Conservation Paintings Specialty Group, Postprints. AIC, 1717 K Street, NW, Suite 301, Washington DC 20006, 61-72.
Koestler, R.J., Sardjono, S., and Koestler, D.L., 2000. Detection of insect infestation in museum objects by carbon dioxide measurement using FTIR. International Biodeterioration and Biodegradation, 46, 285-292.
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.
Landsberger, B., Frauendorf, H., Adler, C., Plarre, R. 2019. ‘Capability and Limitations of Anoxic Treatments for Protecting Museum Collections’, in L. Nilsen and M. Rossipal (eds), Integrated Pest Management (IPM) for Cultural Heritage. Proceedings from the 4th International Conference in Stockholm, pp. 202-210.
Sardjono, S., Koestler, D.L., and Koestler, R.J., 2000. Detection of hidden insects in museum objects by carbon dioxide measurement using FTIR. Student papers: 26th conference of the Association of North American Graduate Programs in Conservation. Smithsonian Center for Materials Research and Education. Washington, D.C., 72-76.
Suzuki, J., and Koestler, R.J., 2003. Visual assessment of biocide effects on Japanese paint materials. In: Koestler, R.J., Koestler, V.R., Charola, A.E., and Nieto-Fernandez, F.E., (Eds.), Art, Biology, and Conservation: Biodeterioration of Works of Art. The Metropolitan Museum of Art, New York, Yale University Press, New Haven, 410-425.
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.
Integrated Pest Management Working Group
Treatment Subgroup March 2008, Updated March 2024