Treatment Experience in Germany

Perhaps the most extensive and creative application of carbon dioxide for pest control has been done in Germany by professional exterminators like Gerhard Binker. Binker is experienced in the use of the conventional toxic fumigants but has also embraced nitrogen and carbon dioxide for a variety of applications. He has designed a series of procedures to meet needs on both small and large scales, from treating movable objects to fumigating sections of buildings where containment involves using portions of the structure itself as container walls. He has even led the way in developing a technology for treating entire buildings with carbon dioxide (Binker 1993a). Binker has developed an expandable gastight chamber, sold commercially as the "Altarion," to deal with movable loads and objects of varying size. The capacity of this unit can be increased by adding chamber elements as needed. Binker claims that the system is able to control and record temperature, humidity, and gas composition for either nitrogen or carbon dioxide treatment of museum objects and archival materials. The system can be operated in locations where other activities are taking place if external gas sen- sors are carefully placed and monitored.

Binker treats infested objects that are very large or cannot be moved—for example, high altars, pulpits, and church pews—by first covering them with impermeable sheeting that is sealed against floor or wall sections and made as gastight as possible. Fumigation with carbon dioxide is then done in a conventional way. Binker found wood-boring beetles to be the major culprits attacking the churches and historic buildings he has treated. Before doing a partial- building fumigation for these pests, it is vital to determine that the rest of the structure is not infested. This is done with a complete and careful examination using established pest management procedures before fumigation is undertaken. It makes no sense to kill off these insects in one part of a building if adjacent areas are also infested.

An excellent example of carbon dioxide fumigation of an entire large building is the Catholic church in Schaeftlarn, Germany, that Binker treated during the

Chapter 8 76

Figure 8.4

Tonnage delivery of carbon dioxide. (Photo courtesy of Gerhard Binker.)

summer of 1995. The volume of space that had to be filled with gas, originally

5 2.31 x 10 3 m , was decreased with air-inflated balloons. This reduced the amount of fumigant that was needed. Still, an enormous quantity of carbon

dioxide had to be maintained at a concentration of 70% over the six weeks of treatment. To meet this need, carbon dioxide in liquid form was periodically delivered by tanker and pumped into a large supply tank. It was automatically withdrawn from the tank and passed through a battery of heat exchangers to convert it to room-temperature gas. A monitoring and control device measured the concentration of carbon dioxide in the church and automatically made up for losses incurred by leakage during the extended treatment period. An unexpected source of leakage was through the floor and out the basement. Overall, a thou- sand tons of carbon dioxide were needed to complete the project (Binker 1996). Figure 8.4 is a photograph showing the magnitude of the carbon dioxide delivery operation. The tanker on the right is unloading carbon dioxide into the main storage tank while a second tanker behind it waits its turn. Two banks of heat exchangers are visible on the left. Throughout the treatment period, the RH ranged from 58% to 70% and the temperature from 19 to 29 °C.

A second example of Binker's work on a large scale is the fumigation of the Catholic church in Salmdorf, near Munich, where an important wooden religious sculpture, the Salmdorf Pietà, is housed (Fig. 8.5). The church was infested with wood-boring beetles, particularly furniture beetles, which had gotten into the

Figure 8.5

altars, pews, pulpit, and organ, as well as into the religious sculpture. After the

Salmdorf Pietà undergoing treatment. (Photo

building was covered with large sheets of poly(vinyl chloride) film, sealed with

courtesy of Gerhard Binker.)

tape, and made as gastight as possible, an additional stormproof tent was con- structed over the church, including the steeple (Fig. 8.6). This was done to mini- mize gas loss and to help retain humidity required for the protection of the wooden artifacts. A temperature and moisture sensor was placed on the Pietà to ensure that dehydration was not occurring. There were heavy rains during the sealing of the church, boosting the RH. Still, additional humidification was required to maintain a moisture level that the operators felt would protect the statues from becoming too dry and cracking. Over the treatment period, the RH ranged from 58% to 70% and the temperature from 19 to 29 °C.

In addition to worries about dehydration, there was concern that the carbon dioxide might change the polychrome of the Pietà. A pigment panel was placed

near the statue during fumigation and later compared to a reference panel. Nei- ther color change nor cracking of the statue were detected. The effectiveness of

Fumigation with Carbon Dioxide Fumigation with Carbon Dioxide

Binker has also demonstrated a very rapid procedure that uses carbon dioxide under pressure for dispatching insects. Objects containing infestations are placed in a pressure chamber and brought to a pressure of 300-600 psig. After two to three hours, the system is depressurized, and 100% mortality is realized. This procedure kills by a mechanism other than dehydration. The cells of insects readily absorb carbon dioxide under pressure; with rapid depressurization, the cell walls burst irreversibly and the insects die. Inert cellulosic material is not damaged by this treatment since it cannot absorb large amounts of carbon diox-

ide. Binker speculates that this procedure may, in the same manner, also kill fun- gal growth (Binker 1993b).

Figure 8.6

Church tented for carbon dioxide fumigation. (Photo courtesy of Gerhard Binker.)

Chapter 8

Appendix A

Conservators

Treatment Experience in Germany