Brief description of treatment
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% for a period of 21 days.
What collections materials can be treated this way?
Most collections can be treated in this manner with the notable exception of materials containing Prussian blue dyes or pigments. Prussian blue is highly susceptible to fading and irreversible chemical change when placed in anoxic environments.
- Construct an enclosure using a low-permeability barrier film such as Marvelseal 360, Aclar, Film-Pak, or Escal or Anoxibug System pre-made enclosures. All seams should be heat sealed and checked for leakage. The enclosure should be made large enough to accommodate a 20% reduction in volume of the enclosed air without damaging the object being treated. Care should be taken not to make the enclosure too large, as this may cause an undesired increase in the equilibrium moisture content of the enclosed object during treatment.
- Place the object within the barrier film enclosure along with enough oxygen scavenger (Ageless or RP or Anoxibug System scavenger (based on oxidation of iron particles) It is common practice to double or even triple the calculated amount of oxygen scavenger required to ensure effective treatment. Some practitioners recommend loosely wrapping the object to be treated in either washed muslin or acid-free unbuffered tissue. Some heat is generated as the oxygen scavenger reacts with oxygen, depending on the rate of the reaction. Care must be taken to spread the packets out and not to place them directly on or next to collections items.
- Carefully pull air out of the enclosure with a vacuum. Seal the final seam of the enclosure. Check the enclosure periodically for shrinkage during the first few days of treatment. If the enclosure has been constructed and sealed properly, a 20% reduction in the volume of the enclosed air mass should be observable by the third to fifth day. Keep the enclosure sealed for 21 days or according to manufacturer directions. After 21 days the enclosure may be opened, and the object can be removed.
Pros and Cons of this treatment
- Relatively simple and inexpensive
- Appropriate for a wide variety of collection materials
- Oxygen scavengers are not registered pesticides; no licensing is required
- Requires a relatively long period for treatment
- Care must be taken to properly construct and seal the enclosure
- Care must be taken to select the proper oxygen scavenger. Some oxygen scavengers contain an added desiccant (e.g. RP Type A), which could decrease the equilibrium
- moisture content of objects during treatment
- Not appropriate for use on materials containing Prussian blue pigments or dyes
- Oxygen scavenger such as Ageless, RP Systems, or Anoxibug System scavenger.
- 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.
- Low-permeability barrier film such as Marvelseal 360, Aclar, or Escal or AnoxiBug system barriers.
- There are pros and cons with each of these materials: Marvelseal is not transparent, so the object is not visible within the enclosure, but it is easier to evaluate the quality of the seal. With the transparent films Aclar, and Escal, the object is visible in the enclosure but it is more difficult to evaluate the quality of the seal because pinholes and gaps are not as visible. Finally, it takes longer to create a seal with Marvelseal than with the transparent films. Some users choose to use two barrier films: a clear film such as Aclar or Escal for the front side so that items and monitors inside the enclosure will be visible during treatment, and an aluminum barrier foil such as Marvelseal 360 for the back side.
Brandon, J. and G. Hanlon. 2003. A low tech method for insect eradication using Ageless. Wooden Artifact Specialty Group Postprints, American Institute for Conservation 31st Annual Meeting, Arlington VA.
Crowther, G and E. Breitung, 2020. Evaluation of low detection limits of a range of low-cost oxygen meters for anoxic treatments
- Ageless oxygen absorber, manufactured by Mitsubishi , is available from several museum supply companies (check the internet for availability.)
- RP system scavengers manufactured by Mitsubishi, is available from several museum supply companies (check the internet for availability.)
- Escal film is manufactured by Mitsubishi (check the internet for availability.)
- Marvelseal is manufactured by Berry Plastics/Covalence Coated Products (formerly Ludlow Corp), and is available from many museum supply companies (check the internet for availability.)
- Aclar film is manufactured by and available from Honeywell International, Inc., Specialty Films; also available from Keepsafe Systems Inc.
- AnoxiBug system is manufactured by Hanwell and available from Cascade Inc.
Integrated Pest Management Working Group
Treatment Subgroup March 2008, Updated July 2020