SULFURYL FLUORIDE (VIKANE): A REVIEW OF ITS USE AS A FUMIGANT
MICHELE R. DERRICK, HELEN D. BURGESS, MARY T. BAKER, & NANCY E. BINNIE
2 VIKANE GAS FUMIGANT
VIKANE WAS developed by Dow Chemical in the 1950s specifically for the control of drywood termites that are typically found in warm climates, such as the southern United States (Dow Chemical Co. 1982). It has since been widely used as a structural fumigant for homes, buildings, construction materials, furnishings, and vehicles for a variety of destructive pests. Studies conducted on Vikane show that it has several advantages, including easy dispersal into a structure, rapid penetration into materials, formation of almost no residues, and ready dissipation after aeration (Meikle and Stewart 1962).
Although Vikane is a gas at atmospheric conditions, it is stored in cylinders as a liquid under its own pressure. For dispersal into a room or chamber, the liquid is released through an application hose or tube toward distribution fans. Volatilization of the liquid occurs rapidly after it is released from the cylinder. This is important, since liquid Vikane is more harmful to objects and materials than the gas and can tarnish metals and damage ceramic tiles. Some precautions, such as fumigating only when the temperature is above 12°C and moving objects out of the direct application path, should be taken to ensure that all the liquid Vikane is volatilized prior to reaching any object. To eliminate this possibility altogether, a heat exchanger may be used to convert the liquid to a gas prior to dispersal. Since Vikane is 3.5 times heavier than air, the air must be circulated at the beginning of the fumigation period to ensure rapid, uniform distribution throughout the fumigation area. After fumigation is complete and the sulfuryl fluoride is released from the building or exposure chamber, the gas moves outward swiftly from the area of containment. From Dow's calculations, it would take less than two hours for 4 g Vikane/m3 in air (962 ppm, a typical dosage for drywood termites [4 oz/1000 ft3]) to be reduced to less than 9 ppm in a house with doors and windows open and a moderate wind (Dow Chemical Co. 1982).
The concentration of sulfuryl fluoride can be monitored during fumigation using a Fumiscope, a thermoconductivity unit that reads from 0.62–1000 g/m3(150–240,000 ppm). The Fumiscope, however, is not sensitive enough to use as a clearing device after fumigation. In order to measure Vikane at a level (5 ppm) low enough to permit safe re-entry into a structure, either of the following monitors may be used: Interscan model GF 1900 pyrolysis unit (0-50 ppm) or Miran 101 infrared gas analyzer (0–150 ppm).∗
∗ Fumiscope. R.K. Hassler Company, P.O. Box 1968, Mammoth Lakes, CA 93546. The units can be purchased through any Dow distributor. Interscan model GF 1900. Interscan corporation, 21700 Nordoff Street, P.O. Box 2496, Chatsworth, CA 91311. The wilks Miran 101 analyzer. Foxboro Analytical, Wilks Infrared Center, 120 water Street, P.O. Box. 449, South Norwalk, CT 06858.
Vikane is a Restricted Use fumigant to be purchased and applied only by licensed fumigators who usually carry special types of insurance for such applications. It is labeled for use in museum chambers by licensed fumigators, either on staff or on a contract basis. Vikane has been used successfully to fumigate some historic structures and their collections, such as the Hearst Castle in California (Pest Control 1977) and the Flagler Mansion in Florida (Moon 1981). The United States, which uses Vikane for 50% of all structural fumigations, and Japan are presently the only countries in which Vikane is registered for use.