A UL rating refers to a product safety classification provided by the UL company. UL tests the safety of appliances and other items. Products that meet UL's standards can carry the statement "UL Listed" or "UL Classified" on its packaging. This statement can include the UL Mark, which in the United States consists of the UL letters printed in black on a white background and surrounded by a black circle.
A product receives a UL certification after undergoing a series of tests. UL uses its own standards along with national standards to evaluate a product's safety and performance. UL may also endorse the components of a particular product without certifying the end product. In this case, the product can state that it contains a UL recognized component. UL does not endorse companies.
An electrical engineer, William Henry Merrill, founded UL as Underwriters Laboratories in Chicago in 1894. UL initially worked on developing standards and safety tests for electrical and fire safety products. The first item to carry the UL Mark was a fire extinguisher in 1904. Since then other items to carry the UL Mark include batteries, cooking appliances and lamps.
UL has expanded its work to include other areas such as food and water quality. It also provides safety training.