This is a common term used to refer to many different types of lights, from a yellow light on a traffic barrier to a red light on the back of a bicycle. Unfortunately, the term is sometimes also incorrectly used to denote Ex luminaires. In the Ex world, we prefer to emphasize the fact that safety is always more than just a single piece of equipment. People, products and places together make (or break) safety.
Short for Underwriters Laboratories. UL are the leading authorities in the United States certifying product compliance with quality, safety and other standards. This includes all Ex-related certifications. Products that have passed the rigorous certification tests get a unique certificate number and permission to use the “UL” label on product.
See also UL. The UL listing is a collection of products that UL, a widely respected certification body, has tested and certified. UL actively maintains this list, meaning it audits products it has already certified and may remove them if the product manufacturer fails the audit.