Hydrogen sulfide has a chemical formula as H2S. H2S is a gas that forms naturally in crude oil, natural gas, and water with high sulfur concentrations (sour water). H2S is soluble in water, and may be released out of the water if there is change in the pH, line pressure, and /or temperature. Some of the process areas may generate potentially fatal concentrations of H2S. These sources could be from raw materials, process reactions, or exposure of materials during a fire. Flare systems handle large volumes of H2S. Any process flare or vent equipment entry could expose personnel to deadly concentrations of H2S. Some streams downstream of refineries may also contain potentially fatal concentrations of H2S. (Contact your local facility safety representatives for a list of specific equipment, which may contain H2S) H2S is a flammable substance, incomplete combustion of H2S may cause the formation of Sulfur Dioxide (SO2). SO2 is also very toxic, and precautions should be taken to avo