Fumigation kills a wide range of insects, arachnids, rodents, fungi, bacteria, and microscopic worms, depending on the type of fumigation and the gas used. The method works because fumigant gases penetrate into cracks, crevices, wall voids, and wood pores that sprays and traps can’t reach, making it one of the few pest control methods that can achieve a complete kill throughout an enclosed space.
Structural Fumigation: Termites and Bed Bugs
The most common reason homeowners encounter fumigation is for drywood termites. Unlike subterranean termites that enter from the soil, drywood termites live entirely inside your walls, furniture, and framing. Because they’re buried deep in wood, surface treatments can’t reliably reach every colony. Whole-structure fumigation solves this by filling the entire tented building with gas that seeps into every pore of the wood.
Bed bugs are the other major structural target. Killing bed bugs with fumigation requires roughly 1.5 to 1.7 times the gas concentration used for drywood termites, because bed bugs are slightly more resistant. But fumigation remains one of the only methods that can eliminate every life stage of bed bugs (eggs, nymphs, and adults) in a single treatment, since the gas reaches inside walls, mattresses, and furniture where bed bugs hide.
Beyond these two primary targets, structural fumigation also kills any other insects present in the building during treatment: cockroaches, carpet beetles, clothes moths, silverfish, wood-boring beetles, and pantry pests. If it’s an air-breathing organism inside the sealed structure, it will not survive.
How the Gas Actually Kills
The most widely used structural fumigant in the U.S. is sulfuryl fluoride, an odorless, colorless gas. It works by attacking the central nervous system. Once inhaled by an insect, the gas is absorbed rapidly and disrupts nerve function throughout the body. For insects, this means paralysis and death, typically within hours at proper concentrations.
This is different from how contact pesticides work. A spray has to touch the pest directly or be ingested. A fumigant fills the entire air volume inside a sealed space, so every organism breathing that air is exposed. There’s no hiding from it, which is why fumigation has such a high success rate for pests that live deep inside structures.
Stored Grain and Food Product Pests
Fumigation is standard practice in agriculture, particularly for protecting stored grain, flour, and other commodities. The fumigant most commonly used in this setting is phosphine gas, and it targets a long list of beetles and moths that infest stored food products:
- Flour beetles (red flour beetle and confused flour beetle), two of the most common pantry pests worldwide
- Lesser grain borers, which tunnel directly into grain kernels
- Saw-toothed grain beetles, a frequent pest in processed foods and cereals
- Khapra beetles, considered one of the world’s most destructive stored-product pests
- Hide beetles and cabinet beetles, which damage stored animal products and dried goods
- Mediterranean flour moths, common in mills and food storage facilities
Phosphine is effective against all life stages of these pests. At concentrations as low as 50 parts per million, eggs from susceptible strains fail to hatch entirely. However, some pest populations have developed varying levels of resistance to phosphine, which is a growing concern in the grain industry.
How Long Fumigation Takes to Work
Fumigation isn’t instant. The gas needs time to reach lethal concentrations in every part of the treated space, and it needs to maintain those concentrations long enough to kill every life stage, including eggs, which are typically the hardest to destroy.
For structural fumigation of a home, the building generally stays sealed and tented for two to three days. Agricultural fumigation timelines vary more widely. Stationary grain containers treated with phosphine and carbon dioxide require a minimum of 24 hours sealed. Metal phosphide treatments need at least 72 hours. For large cargo ships, the required exposure can stretch from 3.5 days to as long as 18 days, depending on how deep the grain is stored in the hold and whether the gas is being recirculated mechanically.
Temperature matters too. Warmer conditions speed up the process because insects metabolize faster and inhale more gas. Bagged wheat flour, for instance, requires 96 hours of fumigation above 68°F but 144 hours at cooler temperatures between 61°F and 68°F.
Soil Fumigation: Fungi, Nematodes, and Bacteria
A completely different category of fumigation happens before planting crops. Soil fumigation targets organisms you can’t see: plant-parasitic nematodes (microscopic worms that attack roots), soil-borne fungi, and harmful bacteria. This is standard practice for high-value crops like strawberries, tomatoes, peppers, and ornamental plants where soil diseases can wipe out an entire harvest.
The specific nematodes controlled by soil fumigation include root-knot nematodes, sugar beet cyst nematodes, root-lesion nematodes, and potato cyst nematodes, among others. These organisms burrow into plant roots, stunting growth and opening the door to secondary infections. Soil fumigants have broad-spectrum biocidal activity, meaning they kill across multiple categories of organisms rather than targeting just one type.
One important tradeoff: soil fumigation also kills beneficial organisms in the soil, including helpful microbes and nematodes that naturally suppress plant diseases. Research has shown that this can lead to rapid resurgence of the very pathogens the fumigation was meant to eliminate, since the beneficial organisms that kept them in check are also gone.
What Fumigation Does Not Kill
Fumigation leaves no residual chemical behind. Once the gas is ventilated from a structure or dissipates from soil, its killing power is completely gone. This means it provides zero protection against future infestations. A home fumigated for drywood termites on Monday can be reinfested by new termites the following week.
Fumigation also does not kill mold in any practical sense. While fumigant gases can kill living mold spores they contact, they don’t remove the mold growth itself or address the moisture problem causing it. Dead mold is still allergenic, so fumigation is not a mold remediation strategy.
It won’t eliminate pest damage either. Termite-damaged wood remains damaged. Fumigation kills the insects currently alive in the structure but does nothing to repair what they’ve already eaten through.
The Shift Away From Methyl Bromide
For decades, methyl bromide was the go-to fumigant for both structural and agricultural uses. It was phased out of production in the United States on January 1, 2005, because it damages the ozone layer. It’s classified as a Class I ozone-depleting substance under the Montreal Protocol.
Limited exceptions still exist. Methyl bromide can still be used for quarantine and preshipment purposes, such as treating wood packaging materials in international trade, and for specific “critical uses” where no feasible alternative exists and the lack of methyl bromide would cause significant market disruption. It cannot be used in residential structures or public food service facilities. Sulfuryl fluoride and phosphine have largely replaced it in most applications.