UL Listing means that Underwriters Laboratories Inc. (UL) has tested representative samples of the product and determined that it meets UL's requirements. These requirements are based primarily on UL's published and nationally recognized Standards for Safety.

There are three variations of UL's Listing Mark:

one used only in the United States, one used only in Canada and one for both the United States and Canada. The C-UL Mark is applied to products for the Canadian market. The products with this type of Mark have been evaluated to Canadian safety requirements, which may be somewhat different from U.S. safety requirements. The optional C-UL-US Mark indicates compliance with both Canadian and U.S. requirements.