Chemicals for Fumigation

Fumigation is an approach to pest control where an enclosed space, such as a room in a house, is filled with a toxic gas in order to kill all pests in that area. It can also be used to kill harmful insects in lumber, grains and other items. There are a variety of chemicals used for fumigation depending on the pest being targeted and other factors. All fumigants are hazardous and must be used with caution under controlled conditions.

The Fumigation Process

• During fumigation, the area being treated will be sealed as tightly as possible. If an entire house is being fumigated, it will be surrounded by a tent structure to keep the fumes inside. Next, a toxic pesticide in the form of a gas is pumped into the area. The amount of gas used is calculated based on the area being fumigated, in order to get a sufficient concentration of pesticide in that space. A chemical fumigant has to have certain properties to be useful. It has to be a gas at room temperature, it has to work quickly to kill pests and it can't attack common surfaces like metals, paints, etc. For obvious reasons, nobody can be in the area while it's being fumigated, and any residual gas has to be flushed out before people re-enter. Most fumigation is carried out using one of a small group of standard pesticides.

Methyl Bromide

• Methyl bromide, or bromomethane, is a colorless gas at room temperature. It is a good broad-spectrum fumigant that will kill a wide variety of pests including insects, rodents and even weeds. Until fairly recently, it was very widely used for fumigation purposes. In 1991, for example, almost 20 million lbs. were used in California alone. However, methyl bromide was recognized as an ozone depleting chemical and was phased out under the Montreal Protocol. It was phased out completely in the United States as of 2005 except for a few specific exemptions.

Sulfuryl Fluoride

• Sulfuryl fluoride is a fumigant originally developed by Dow Chemical and is widely used for termite control in residences. It is a colorless gas at room temperature and must remain in the area being treated for one to three days to be effective. It has taken over from methyl bromide in some applications since it does not deplete the ozone layer, although it is likely a contributor to global warming when released into the atmosphere.

Chloropicrin

• Chloropicrin, or trichloronitromethane, is a colorless liquid that evaporates when released into air. It was first synthesized in the 1800s and was used in World War I as a chemical warfare agent. In the past it was used to kill pests on grain and other foods, but this has largely been discontinued due to concerns about toxic residues left on the food. It is now mostly used to kill worms and fungi in soils.

Phosphine

• Phosphine, or hydrogen phosphide, is an odorless, colorless gas. Phospine is used for the fumigation of grains and is very effective in this role, although it can require up to 10 days of fumigation to completely kill all pests. Phosphine has taken over some of the functions of methyl bromide. There have been reports, however, of some pests developing resistance to it.