Technical References


UL Listed vs. UL Classified vs. UL Recognized


The three categories that Underwriters Laboratories uses to rate products are:
  • UL Listed
  • UL Classified
  • UL Recognized

UL Listed

A product is UL Listed after it successfully completes a series of mechanical, electrical, and thermal characteristics test which simulate all reasonable, foreseeable hazards.

UL Listed is assigned exclusively to the product for the specific applications for which it was tested and is not valid for other applications.

UL Classified
A product is UL Classified after it is evaluated and passes tests for one or more of the following:
  • Specific hazards only
  • Performance under specified conditions
  • Regulatory codes
  • Other standards, including international standards

The UL Classified rating is generally restricted to industrial or commercial products.

UL Recognized
A product is UL Recognized after it is tested for use as a component in a UL Listed package and passes. These component products are tested for electrical, mechanical, and thermal characteristics.

UL Recognized is a more general-purpose approval than UL Listed because it allows a product to be certified for a category of equipment uses. An example is hookup wire, which is UL Recognized as appliance wiring material, a category of uses that includes:
  • Data communications
  • Telecommunications
  • Instrumentation