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Carbonyl sulfide (COS) is a colorless, flammable gas with industrial uses, including as an intermediate in herbicide production. It is also found in petroleum products and released by volcanoes and trees. COS is a major source of atmospheric sulfur corrosion and considered a pollutant by the EPA. It can cause narcotic effects, skin and eye irritation, seizures, and death in high doses. It is highly flammable and emits toxic gases when burned. Removal of COS is the subject of several patents.
Carbonyl sulfide is a chemical compound of carbon, sulfur and oxygen, with each molecule containing one atom of each element. It has the chemical formula OCS but is commonly written COS. It is a colourless, flammable gas with an unpleasant sulfur smell. It has several industrial uses, but is most commonly used as an intermediate in the production of organic herbicides.
The main uses of carbonyl sulphide are in the production of organic herbicides; in the production of other chemicals, such as organic sulfur compounds; and as a fumigant. It is a byproduct of carbon disulfide production. Carbonyl sulfide hydrolysis is a process that produces hydrogen sulfide, which is used to produce sulfuric acid. It is also used in the production of a class of chemicals called alkyl carbonates.
Carbonyl sulfide is also found as an impurity in some petroleum products, as well as refinery byproducts. It is also found in the exhaust gases of some fuels that contain sulfur. It also occurs naturally and is released into the air by volcanoes, swamps and in small quantities by many types of trees.
According to the World Wide Science Organization, carbonyl sulfide is a major source of atmospheric sulfur corrosion of metals such as copper and bronze, among others. It is considered by the United States Environmental Protection Agency (EPA) a pollutant under the Clean Air Act. According to the EPA, more than 16 million pounds (about 7.2 million kg) were released into the air in the United States in 1992 and information suggests that recent amounts may be higher.
Little research has been done on the direct toxicity of carbonyl sulfide to humans, but the EPA reports that in sufficient quantities, inhalation can cause narcotic effects in humans and is irritating to skin and eyes. Other data suggest that high doses can cause seizures and death from respiratory failure. A study in rats showed that exposure to carbonyl sulphide over a period of time can be fatal to some animals.
Carbonyl sulphide is classified as a fire hazard and is highly flammable and potentially explosive when exposed to flame. Acceptable methods of extinguishing fires are carbon dioxide, water spray and dry chemical extinguishers. When burned, it emits high levels of carbon monoxide, a poisonous, colorless and odorless gas, as well as hydrogen sulphide, which is also a toxic material.
Once considered relatively harmless, carbonyl sulfide is now considered undesirable as a component of many fuels, refinery products and by-products. The removal of carbonyl sulphide is the subject of several patents. Many companies use the process to remove this harmful substance from products such as propane and natural gas.
