PH₃, or phosphine, is a colorless, flammable gas with a distinct odor resembling that of rotten fish. It consists of one phosphorus atom bonded to three hydrogen atoms. Phosphine is primarily used in the semiconductor industry and as a fumigant in agriculture to control pests. In nature, phosphine can be produced by anaerobic bacteria during the decomposition of organic matter. It is also found in trace amounts in the atmosphere of Jupiter and Saturn, where it may indicate the presence of biological processes. Due to its toxicity, proper safety measures are essential when handling phosphine.