Diesel Exhaust Fluid (Retail) is a specialized industry that involves the retail sale of diesel exhaust fluid (DEF) to consumers. DEF is a non-toxic, colorless, and odorless solution that is used in diesel engines to reduce emissions of nitrogen oxides (NOx). The industry is a subset of the Gasoline Service Stations (Retail) industry and is classified under SIC Code 5541. Diesel Exhaust Fluid (Retail) businesses typically operate at gasoline service stations or truck stops. They sell DEF in bulk or in packaged containers, such as jugs or drums. The industry is heavily regulated by the Environmental Protection Agency (EPA) and other government agencies to ensure that the DEF sold meets the required quality standards. The demand for DEF has increased in recent years due to the implementation of stricter emissions regulations for diesel engines. As a result, many diesel engine manufacturers now require the use of DEF in their engines to comply with these regulations. This has led to a growing market for DEF and an increase in the number of businesses that sell it.