1 INTRODUCTION

BY DEFINITION, a fumigant is a toxic, gas-phase, chemical agent that is lethal to pests, insects and/or micro-organisms (Hawley 1987). This implies several aspects of the fumigant and its properties:

1. the chemical reactivity of a fumigant may cause it to react not only with living organisms but with other materials with which it comes in contact
2. the penetration and/or absorption of the fumigant into a material depends on its solubility and may be affected by the gas distribution and the environment within the exposure area
3. the biocide effect of the fumigant depends on the type of infestation and the concentration and length of time that the pest is exposed, and
4. the fumigant is likely to be directly toxic to humans in the gas phase and may also leave harmful residual compounds in the fumigated artifact.

A comprehensive assessment of the above aspects of a fumigant, along with its methods of use, aids in its selection as an option for the eradication of pests from an object or building and should be made prior to its use.

An ideal fumigant for insect pests would penetrate rapidly into infested areas, effectively kill all stages of development of the organism, remain nonreactive to the material being fumigated, and disappear completely from the fumigated materials upon aeration. This degree of selectivity is rarely the case; in fact, most fumigants that have been or are currently in use by museums do alter materials to varying degrees (table 1). For example, methyl bromide reacts with sulfur-containing materials such as furs, hair, feathers, and leather goods producing a malodorous product (Dow Chemical Co. 1957). Phosphine, hydrogen cyanide, carbon disulfide, and dichlorvos react with metals and some pigments (Monro 1972), and thus any material containing a metal, such as a weighted fabric or a mordanted dye, may be susceptible. Ethylene oxide has been found to react with cellulose and proteins and to leave carcinogenic residues in fumigated materials (Ballard and Baer 1981; Green and Daniels 1985; Florian 1987).

Table 1 Some Fumigants Used in Museums and Their Reactivity with Various Materials

Faced with these problems, conservators have been seeking alternative methods to fumigation. Approaches have been made to bypass toxic chemicals in favor of methods that prevent infestations, such as integrated pest control management programs (Parker 1987), or by using less problematic methods of killing pests, such as freezing (Florian 1987; Nesheim 1984) and oxygen deprivation using carbon dioxide (Sanders 1987) or nitrogen (Ali Niazee 1972; Valentin and Preusser 1989). However, these methods are still in the process of being evaluated and are suitable mainly for movable artifacts and not for the treatment of buildings, with or without their contents. Thus, some cases may require a chemical fumigant that can be used either in situ or in gas-tight chambers and that does not cause unacceptable changes in museum materials.

One possibility is sulfuryl fluoride, a fumigant manufactured by Dow Chemical Company and sold under the name of Vikane. In recent field studies and structural fumigations using Vikane, little or no damage to the fumigated material has been observed. Therefore, sulfuryl fluoride has been selected for an in-depth study to determine what unobservable effects, if any, Vikane may have on materials commonly found in museums.

This review article is the first step in a program developed to provide conservators with specific, detailed information on the use of Vikane, and it forms a basis for the evaluation of sulfuryl fluoride. An extensive study on the effects of Vikane on various materials and its suitability for use in museum chambers and structural fumigations is being conducted by the Getty Conservation Institute (GCI) in conjunction with the Canadian Conservation Institute (CCI) and the Smithsonian Institution's Conservation Analytical Laboratory (CAL). Also, through a contract with GCI, a group at the University of Florida is reevaluating fumigant concentrations recommended for structures to determine the lowest levels that may be used in controlled museum applications. While some preliminary results of these projects will be discussed in this paper, the conclusions and supporting data regarding the use of sulfuryl fluoride on museum materials will be published in subsequent articles. The annotated bibliography of the Vikane literature, developed during this study, is available upon request from the Scientific Department, GCI.