UL Listing and Classifcation Explained

What is UL Listing an UL Certified?

U.L. listing and classification are stated throughout the worldwide construction market, but it seems many people are in the dark about what they are and the difference between the two. This post explains the background behind U.L and what it means for the products you are using in your buildings…

Who is U.L.?
U.L. (Underwriters Laboratories) is an independent, not-for-profit product safety testing and certification organization, founded in 1894. Over the last century, Underwriters Laboratories has become the world’s best known independent product safety certification organization. Millions of products and their components are tested to UL’s rigorous safety standards.

What is “Listed”?
A published list stating the product has been tested to and complies with the applicable Standard and maintains periodic inspection to assure production of the listed products are in accordance with the listing. Having UL Listing guarantees that the product fully complies with each and every one of UL’s requirements in the applicable Standard, and the manufacturer’s product can then bear the UL Mark.

Third Party Certification
The UL listing is called a “Third Party Certification”. This certification provides an unbiased safety assurance to interested parties including the manufacturer, the specifier, and the consumer. UL’s field reps worldwide conduct periodic, unannounced on site inspections of UL-certified products in the manufacturer’s factory. The product is verified as being fully compliant with a set of rules governing the product. Another part of the agreement is traceable labels. Each product listed must have a label affixed to the product traceable to the manufacturer through Underwriters Laboratories.

Listed and Classified Products
They are not the same, in fact Classified products have been evaluated only for specific properties, a limited range of hazards, or suitability for use under limited conditions. If a product is Classified by UL, this can mean its testing meets the particular requirements for a single test with a published result, but has nothing to do with all the other tests that may form part of a Standard (i.e., UL 181).

UL Listing and Compliance
Also, if products comply to some parts of specific UL Standard, this can mean their testing only meets that part of the Standard, but the products do not fully conform with the UL requirements.

Only after a manufacturer has successfully passed all tests within a given Standard can it then be Listed.

Online Certifications Directory
The Online Certifications Directory includes the names of companies authorized to use the UL Mark on or in connection with products in compliance with UL’s requirements. If you wish to view that a product is UL Listed, then either use the web address www.ul.com and the Online Certifications Directory tab searching for a company name e.g. Kingspan or UL file number, alternatively type in the link below or search company name e.g. ‘Kingspan’.


The Kingspan KoolDuct System is UL Listed as a Class 1 Air Duct, to a Standard for Safety UL 181 (underwriters Laboratories: Factory Made Air Ducts & Air Connections, when fabricated to a specification clearly defined by UL. Please follow the link for more information


All consultants and engineering professionals concerned with performance and safety in buildings, and in particular in air ductwork, can take comfort that the specification of UL Listed Products ensures that those products meet a comprehensive Standard and that independent UL inspectors perform regular follow up factory inspections to ensure product consistency.


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Kingspan Insulation is a market leading manufacturer of optimum, premium and high performance rigid insulation products and insulated systems for building fabric and building services applications.

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