Fumigation

Fumigation is a specialized method used for pest control or the removal of harmful microorganisms. This process works by completely filling a specific area with gaseous pesticides, which are known as fumigants. These gases function by suffocating or poisoning the pests within the target space.

This technique is vital for protecting buildings, soil, grain, and various food products. It is also used during the import and export of goods. This helps prevent the transfer of exotic organisms between different regions of the world.

The mechanism of fumigation follows a very strict sequence of phases. First, all humans must be evacuated from the target area. Next, the space is sealed to create a completely enclosed environment. The fumigant is then released into this sealed space. The area is held for a set duration to allow the gas to percolate through everything. This ensures the gas reaches every part of the infestation. Finally, the space is ventilated to allow the poisonous gases to escape. This ventilation step renders the area safe for humans to re-enter.

There are two primary types of fumigation: structural and commodity. Structural fumigation targets pests inside buildings, such as residences. This includes pests that live inside the physical structure, like woodborers or drywood termites. Commodity fumigation is conducted inside a physical structure, like a storage unit. However, its goal is to eliminate pests from physical goods. This usually involves food products held within containers.

A common method for residential buildings is called tent fumigation. In this process, workers place a large tent over the entire structure. These tents are typically made of plastic or PVC-coated canvas material. The tent creates a seal that contains the poisonous gases and prevents them from escaping into the environment. This is often used to treat bedbugs or drywood termites. One common pesticide used in tenting is sulfuryl fluoride. This is a naturally occurring gas used at much higher concentrations than what is found in the atmosphere. It is useful because it leaves no physical residue behind.

Different environments require different chemical agents. In hospitals, formaldehyde fumigation is a recognized and common method for maintaining microbiological cleanliness. It is often used because it is a cost-effective procedure for operating theatres. Another option is vaporized hydrogen peroxide, which is a dry gaseous method. This is used for room decontamination and aseptic processing isolators. For example, to treat a 1,000 cubic foot area, a 20% solution can be used. This solution consists of 200mL of agent in 1,000mL of demineralized water. The fogger sprays this for 30 minutes, with a contact time of at least one hour.

Many different chemicals are used, each with specific properties. Methyl bromide is a gas with a boiling point of 4.3 °C, but it is restricted by the Montreal Protocol. Ethylene oxide is used for food and has a boiling point of 10.7 °C. Phosphine gas, which has a boiling point of -87.7 °C, is used in grain silos to kill rodents and insects. Some chemicals are no longer used because they are dangerous. For instance, ethylene dibromide and methallyl chloride are carcinogenic. Hydrogen cyanide is considered extremely toxic, and formaldehyde is both carcinogenic and explosive.

Safety is the most critical aspect of this hazardous operation. Because these chemicals are toxic to most forms of life, operators must hold official certification. This legal requirement ensures that only trained professionals handle the gases. Post-operation ventilation is also a vital safety step. It is important to distinguish between the source of the gas and the environment itself. Even if the fumigant pack is spent and safe, the space will still hold gas until it is properly ventilated.