The chemical formula for phosphine is PH3. The compound has a trigonal design with the lone phosphorous atom at the apex, or top, surrounded by three hydrogen atoms forming the base of the 3-dimensional triangle form. Phosphine is also known as phosphane, and is a colorless, odorless, flammable gas. Although it typically is odorless, it may, in concentrations, have a particularly noticeable garlic smell, due to the phosphorous presence. Phosphine is not to be confused with phosgene, which is a totally different molecular compound. Phosphorous is known for its ability to oxidize with oxygen in various types of combustible reactions. Phosphorous comes in two forms, white and red, and both react with oxygen to provide luminous combustion quite readily. Red phosphorous is used to manufacture matches, and has a quite recognizable odor when burned.