Phosphine gas is a colorless, flammable gas with a distinct, unpleasant odor similar to that of rotting fish. Its chemical formula is PH3, and it consists of one phosphorus atom bonded to three hydrogen atoms. Phosphine is primarily used in the semiconductor industry and as a fumigant for stored grains. In the environment, phosphine can be produced naturally through the decomposition of organic matter. It is also a byproduct of certain industrial processes. While it has applications in agriculture and manufacturing, phosphine is toxic to humans and can pose serious health risks if inhaled in significant quantities.