One of our readers recently asked “When you fumigate, are all of the gaseous pesticides absorbed into the ground or when the tents come down do the gases get let into the air? Also if the gases are released into the air, do you know how harmful for the environment that can be?”

Good question but it’s a little tricky to answer.

Each fumigation is different; the conditions at the time of the fumigation determine where the gases go and at what percentages. I’ll try to give a very rough summary.

A lot depends on the environmental conditions at the time of the fumigation; the moisture content of the soil and temperature determines the amount of gas absorbed into the soil. The temperature of the air and relative humidity greatly affect the amount absorbed into the atmosphere when the tent is on and also determines the amount of gas injected into the structure.

A little less than 50% of the gas is dissipated when the tent is in place. When the tent is removed, a natural aeration period begins and allows the remaining gas to escape into the environment.

We suggested our reader contact the main fumigant suppliers for a more detailed answer…if you’re looking for some more detail we suggest you contact the companies below.

Dow AgroSciences

Drexal Chemical Company 

Also be aware, don’t expect a definite answer. There’s a lot of debate about the impact on the environment and very little quantifiable data. Much of the pro/con data is interpretive so always consider the source of the information.

Fumigation also known as tenting, is a method of pest control that completely gets rid of pests within the area being fumigated.

The pests are eradicated with the use of pesticides in gas form. Methyl bromide used to be the most widely used pesticide in tenting but has since been restricted because of its environmental damage. Nowadays there are several fumigants that can be used including formaldehyde, methyl isocyanate and hydrogen cyanide.

The structure is either sealed with plastic, tape or other materials or the entire structure is tented with the use of nylon tarps. See pic above. The length of fumigation or tenting can vary from a couple hours to a week; depending on the pest problem and the size of the structure.

It’s important to remember that the pesticides used to kill the termites can also kill or poison other living things. All people, pets (fish included), plants, etc… are to be removed. Also, it’s a good idea to remove or completely seal anything that will eventually be ingested (pills too!).

Proper precautions are taken when it comes to fumigation. For instance, the re-entry date, time and other information will posted on the house when the structure is safe to re-enter. But, if headaches, nausea or any other symptoms appear after re-entering the structure, leave immediately and contact a doctor or poison control.

For more in depth information about fumigation, view California’s Structural Pest Control Board’s FAQ about fumigation.

Fumigation is an aggressive method of pest control but it’s not flawless. Since the pesticide used is in gas form, there is no poison left behind so the termites or other pests can return. Also, the deadly dosage of pesticide for one pest may not be enough to kill another pest. But if fumigation is performed correctly, the target pest should be eradicated.