Carbonyl sulfide (COS) is a colorless, odorless (when pure) relatively stable gas with a boiling point of -50°C.
There are limited commercial uses of COS. It is produced only in small quantities and used for small-scale experimental purposes and as an intermediate in the synthesis of organic sulfur compounds, thiocarbamate herbicides, and alkyl carbonates. 

Uses

Pesticide manufacturers are believed to be the largest users of COS. Similar to CS2, research conducted by the Stored Grain Research Laboratory at the Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) has shown COS to be an effective soil and grain fumigant for controlling insects on crops such as wheat, barley, oats, and peas, although it is not currently approved for this commercial use.

The use of COS as a fumigant for durable commodities and structures was patented worldwide in 1992 by CSIRO Australia. COS has the potential to replace methyl bromide, being phased out due to its ozone depletion properties, in several of its applications for durable commodities and also to be used as an alternative to phosphine when there is a significant problem with insect resistance.

Environmental Fate

Most of the releases of COS to the environment are to air, where it is believed to have a long residence time. Its half-life in the atmosphere is estimated to be approximately 2 years. It may be degraded in the atmosphere via a reaction with photochemically produced hydroxyl radicals or oxygen, direct photolysis, and other unknown processes related to the sulfur cycle. Sulfur dioxide, a greenhouse gas, is ultimately produced from these reactions. COS is relatively unreactive in the troposphere, but direct photolysis may occur in the stratosphere. Also, plants and soil microorganisms have been reported to remove COS directly from the atmosphere. Plants are not expected to store COS.

COS is extremely mobile in soils. If released to soil, it will volatilize quickly to the atmosphere (Koc= 88). It has a high solubility in water and will not readily adsorb to soil particles, sediment, or suspended organic matter. Therefore, COS is expected to volatilize rapidly from soil and water or, depending on volume, concentration, and site-specific characteristics (e.g., soil type, depth to groundwater, temperature, and humidity), maybe able to move rapidly through the ground and impact groundwater. COS may be hydrolyzed in water to form H2S and CO2.
COS is also actively taken up by some plants and converted to CS2; that is, the atmospheric pathways are reversed, and soils may act as both a net source and a net sink for COS depending on the concentration of COS and the characteristics of the soil. COS is therefore accurately described as a naturally occurring and widely distributed chemical found or produced in the air, soils, live and decomposing vegetation, and food.

Toxicity

Toxicity from exposure to COS is likely the result of its decomposition to CO2 and H2S. H2S inhibits respiration at the cellular level, causing methemoglobinemia, which inhibits the cytochrome oxidase system, causing cytotoxic anoxia. In one study, rats treated with acetazolamide, an inhibitor of carbonic anhydrase, showed lower blood levels of H2S following exposure to COS and exhibited decreased toxicity. H2S is believed to be primarily responsible for many of the reported adverse effects associated with exposure to COS.

COS reacts readily with ammonia and primary amines to form ammonium thiocarbamate and amine salts of monothiocarbamic acid, respectively. Reaction with two primary amines may result in the formation of H2S and linking of the two amines via a carbonyl group reaction, suggesting considerable potential for protein cross-linking by COS in vivo, and this has been proposed as a mechanism to explain occupational neuropathy observed with CS2, and predicted for COS.