What’s the “tea” about Anoxia Treatments?

When I started an internship in San Francisco, California, I had no idea what to expect while working in a private conservation studio. One of my first big tasks when I arrived was to help open the large anoxia tent that was set up downstairs. This large, silver tent was roughly twenty feet long by seven feet wide by seven feet tall. Pretty intimidating since I didn’t know what I was looking at exactly. I still wasn’t sure what to expect.

We set up a ventilation system, opened doors and windows, and turned on monitors that indicate the different levels of gas in the air. A large 3-sided door was carefully cut in the front of the tent to expose the approximate 150 paintings, rugs, and tapestries that had been waiting inside for roughly eight weeks. As soon as the door was opened, the monitors started beeping, indicating the levels of oxygen were too low. We had to leave the room until it was safe to return, which took about an hour for the CO₂ that filled the tent to dissipate.

The question that might still be going through your head, like it was in mine, is “but what is it?”. An anoxia treatment is where an item (or in this case, many items) that has been infested with pests, fungi, or bacteria can be placed in a closed environment and the oxygen reduced to less than 0.1% for four to six weeks, or even longer, using nitrogen or CO₂. The time can depend on how many items being treated and their condition. (Daniel, V. and Hanlon, G) During this process, the pests and fungi/bacteria spores are starved of oxygen and die. This process is non-invasive and can be used on practically all materials and even fragile items. (Museumpests.net) By using this method, the conservator is not introducing cleaning chemicals or pesticides into the initial treatment which can have an effect on the physical properties of the artifact, such as fading, staining, deterioration, shrinkage or swelling. (Grandinett) Even though using this method takes longer than most alternatives and can be more expensive, it does ensure that the pests, fungi, or bacteria are killed, if used properly.

The method behind this practice will affect objects infested with pests, fungi or bacteria in the same way. Pests, fungi and bacteria are living organisms needing oxygen to survive. When they are exposed to an environment where there is no oxygen, they starve. Some pest species have been known to reanimate after being in an anoxic atmosphere for hours or even days. That is why it is important that these treatments need to be done over many weeks. (Maekawa)

Anoxia chambers do not always have to be as big as the first one I encountered. The reason why that one was so large was because the studio I was working at had multiple clients that had been affected by pests or mold. In some cases, a smaller sized chamber can be made for one item or slightly larger for multiple items. Essentially, it all depends on how many objects you will be working with.

There are two different styles of chambers that can be used. There are hard wall chambers and soft wall chambers. A hard wall chamber is a steel structure, typically with shelving to place objects on, a secure door, and pumps where the gas can be safely injected into the chamber. (Micrographicsdata.com) These chambers vary in size and can be on the pricey side, but they can be reused over and over again. A few downsides to using a hard wall chamber would be the restriction on the size of the item that can be placed inside the chamber and the storage of the chamber when not in use.

A soft wall chamber can either be purchased or made on an “as needed” basis. A soft wall chamber can be purchased in a similar fashion to the hard wall chamber. These will come in different sizes, just like the hard wall chamber. One difference would be the lack of an internal structure to the chamber, so shelving for objects and an internal framework would have to be placed inside by the user if necessary. Just like the hard wall chamber, the soft chambers can be reused multiple times but is more easily stored when not in use. (Maheu-maheu.com)

There is also a way to create your own chamber. To do this, you would need an impermeable barrier film (such as Marvelseal®), a heat sealer, oxygen-absorber sachets, and CO₂ or nitrogen. By making your own chamber, it can be made any size you’d like and accommodate as many items as needed. When making a chamber for one item, you would want to make it slightly larger than the item itself to allow the gas to surround the item. After cutting two pieces of barrier film, these pieces need the edges sealed together using heat to ensure the gas does not leak out. Once most of the edges have been sealed, the item and sachet can be placed inside. The sachets are used to absorb additional oxygen and moisture within the chamber. The final edges will be sealed, leaving a small area which needs to be large enough to fit the nozzle of the canister of CO₂ or nitrogen. Once the gas has been flushed into the chamber, inflating it, the nozzle can be removed and the final section of film can be heat sealed. If the chamber was purchased, the steps would start with placing the item and sachet into the chamber. There are flammable gas detectors available to check for leaks once you are finished sealing the chamber. The soft wall chambers will stay slightly inflated and that will help to protect the items while inside the chamber. (Burke) After four to six weeks has passed, open the chamber in a well-ventilated area, and your object will be ready for the next step of treatments.

If pests, fungi, or bacteria come to be a problem in a collection at home or in a professional setting, it is important to know how to handle the situation and what your options might be. Seek out a local conservator that may offer these services or do your research before setting up your first chamber, if that is your profession.

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Sources Cited

Burke, J. (1999). Anoxic Microenvironments: A Treatment for Pest Control. [online] Nps.gov. Available at: https://www.nps.gov/museum/publications/conserveogram/03-09.pdf [Accessed 27 Feb. 2020].

Grandinett, M., Wagner, J., Campbell, B. and Hobbs, L. (2020). Mold and Pests in the Library. [ebook] Available at: https://library.princeton.edu/sites/default/files/Mold%20and%20Pest%20Training%20Presentation_1.pdf [Accessed 2 Mar. 2020].

Maekawa, S. and Elert, K. (2003). The use of oxygen-free environments in the control of museum insect pests. Los Angeles, Calif.: Getty.

Maheu-maheu.com. (2020). Fumigation Bubble – Maheu&Maheu – Pest management. [online] Available at: https://www.maheu-maheu.com/Products/Fumigation-Bubble [Accessed 1 Mar. 2020].

Micrographicsdata.com. (n.d.). https://www.micrographicsdata.com/wp-content/uploads/2019/08/MD_EXPM6_Anoxia_Chamber_standard.pdf. [online] Available at:

Click to access MD_EXPM6_Anoxia_Chamber_standard.pdf

[Accessed 2 Mar. 2020].

Museumpests.net. (2020). Solutions – Nitrogen/Argon Gas Treatment | Museumpests.net. [online] Available at: https://museumpests.net/solutions-nitrogenargon-gas-treatment/ [Accessed 1 Mar. 2020].

Daniel, V. and Hanlon, G. (1993). Eradication of Insect Pests in Museums Using Nitrogen. [online] Cool.conservation-us.org. Available at: http://cool.conservation-us.org/waac/wn/wn15/wn15-3/wn15-307.html [Accessed 3 Mar. 2020].