Pest Treatment Case Study: Carbon Dioxide Treatments at Historic New England Overview

Originally developed for the food and grain industry, Carbon Dioxide (CO2) treatments (sometimes also referred to as modified or controlled atmosphere treatments) have been safely adapted for use in museums and other collecting institutions. Historic New England continues to use other forms of treatments such as low temperature/freezing, and low-tech heat treatments. However, CO2 is preferred for the following reasons:

• Historic New England has an existing CO2 treatment facility located at the collections and conservation center in Haverhill MA.
• The interior area of the treatment chamber is 1,000 cubic feet and can accommodate large objects.CO2 gas is inert with no residue or carry over effects on collections
• Cost of operation is lower working in larger volume of treatment.
• Objects can be safely returned to storage immediately after treatment.
• The cost of CO2, energy and maintenance is reasonable after initial equipment purchase and facility set up. In house staff time is minimal during treatment cycle.
• With proper training, treatments can be done by staff without need for special permit or license depending on local and federal regulations. Note that some states in the US require a pesticide operator’s license for all users.

Background

Historic New England follows guidelines for using CO2 to treat pest infested collections based on the Getty Conservation Institute’s 1998 Inert Gases in the Control of Museum Pests. This publication, based on over 25 years of experience using the system, includes technical data and information on mortality rates, and results of several research studies. Historic New England also has over 25 years operational experience with the CO2 system and has run nearly consecutive cycles since 1992. The length of treatment time depends on temperature 80 degrees F plus or minus 5 degrees is ideal and insect species. A consistent range of 60-80% CO2 (corresponding to 4- 6% oxygen) is ideal. During the treatment process, the CO2 levels may drop over a 2 to 4 week period; if so, additional CO2 can be introduced to raise the concentration. A 14 day treatment is sufficient if an internal temperature of 80 degrees F and a CO2 concentration of 60-80% are maintained. A 21 day treatment would be required at room temperature (approximately) 68 degrees F. Running time can be adjusted to insure mortality for more resistant species, heavy infestations and dense oversized objects.

Treating collections with carbon dioxide

Historic New England has 37 primary historic house sites, and a collection of more than 80,000 oversized objects. The collection includes furniture, architectural fragments, and large rugs. After a bad infestation of webbing clothes moths and furniture beetles at one site and a concurrent moth infestation in a storage area at another facility, the museum chose to purchase a standard commercial Rentokil CO2 unit (a chamber constructed with a PVC membrane and an interior framework), in 1992. This type of bubble has an average life span of 10 years. A new membrane or ‘bubble” manufactured by the Maheu & Maheu Company was installed in 2002 and a third generation bubble was purchased and installed with a systems upgrade ten years later. A smaller, more flexible bubble system was also purchased at this time. Having an in-house CO2 bubble unit made it possible to treat oversized collections and large volumes of material on a regular, monthly cycle. It also proved to be cost-efficient for outside service vendors. Historic New England currently offers treatment services to outside clients including neighboring museums, galleries, auction houses and private clients. Once objects have been treated, they can be safely and immediately returned to storage areas and clients.