Hydrogen sulfide is a colorless chalcogen hydride gas with the characteristic foul odor of rotten eggs. It is found it many gases such as the volcanic gases, natural gas, and in some sources of well water. We also produce a small amount of it and use it as a signaling molecule, it is also a flammable gas. Hydrogen sulfide is mainly used to produce sulfuric acid and sulfur, but it is also used to create pesticides, leather, dyes, and pharmaceuticals. It is also used to make heavy water for nuclear power plants.