Zinc phosphide is an inorganic chemical compound that combines zinc and phosphorus, and it is often used as a rodenticide. Once eaten and exposed to stomach acid, it releases a toxic phosphine gas that kills rodents.
The smell of rodenticide that contains zinc phosphide is attractive to rodents, but it is repulsive to other mammals. Birds are also not sensitive to its smell. Zinc phosphide often works to control rodents that are immune to other common poisons. It works because the phosphine gas produced stops heart, lung and liver cells from producing energy. Zinc phosphide is toxic to humans and other animals. Anyone exposed to it should follow the first aid instructions on the product's label and call a poison control hotline.