Fumigation is a method of pest control that completely fills an area with gaseous pesticides to suffocate, poison, or otherwise kill the pests within. It is used for control of pests in buildings, the soil, and food stuffs. In the maritime industry, fumigation is used to kill pests in grain and other food stuffs being imported or exported – both to preserve the quality of the cargo and to prevent the transfer of nonindigenous species. Fumigation in the maritime industry is regulated by the International Maritime Organization (IMO) and by flag states and port states. Marine insurers are also involved, providing guidelines for the safe and proper use of marine pesticides. There are a variety of pesticides in use in the maritime context. Phosphine is widely used to fumigate bulk and bagged grain cargoes. It is a colorless, flammable, toxic gas, and must be handled with great care. Phosphine is most commonly available in pellet form packed in cylindrical tubes. The tubes are placed in the cargo. As they disintegrate, the pellets come into contact with atmospheric water and the gas is released. Pests, such as rats and insects, that are in the presence of the gas quickly die. On large bulk carriers, the gas often does not penetrate all the way down to the bottom, leaving pests in that location undisturbed. To overcome this situation, some ships are equipped with a special piping system that can pump phosphine gas from the air space above a closed cargo hold down to the bottom of the hold, where it rises through the cargo to provide for more thorough penetration. Other fumigants, such as SO2, are used in shipping containers. Detailed information on the selection and use of marine fumigants is available in two IMO publications: MSC.1/Circ.1264 – Recommendations on the safe use of pesticides in ships applicable to the fumigation of cargo holds; and MSC.1/Circ.1265 – Recommendations on the safe use of pesticides in ships applicable to the fumigation of cargo transport units.