UL (Underwriters Laboratories)
The testing lab whose listing marks show a product was evaluated to a safety standard.
Quick Answer
UL (Underwriters Laboratories) is a safety science organization that tests and certifies products against safety standards. A UL listing means a product was evaluated and is included in the lab's published directory. On construction projects, specifications require UL listings for electrical equipment and for fire-rated assemblies, and reviewers check them in submittals.
The Full Picture
UL is a testing, inspection and certification organization. Its own site describes it as a global leader in applied safety science, offering testing, inspection and certification, with certification marks recognized in many countries. UL has operated for well over a century, and its name is on a wide range of products, from electrical devices to building materials.
A listing is different from a general claim of compliance. In OSHA's electrical definitions, listed equipment appears on a published roster from a nationally recognized laboratory that periodically inspects production of that equipment, and the roster states the equipment meets recognized standards. Labeled equipment carries the laboratory's mark. OSHA's Nationally Recognized Testing Laboratory program recognizes private organizations to certify products to OSHA's electrical standards, and a certified product bears the laboratory's registered mark. Whether a given lab is recognized, and for which standards, is stated by OSHA, so the current list should be checked.
In construction, UL listings come up in two places. The first is electrical and similar equipment: panelboards, fixtures, cable, fire alarm devices and other products, which specifications require to be listed so the inspector can accept them. The second is fire-rated assemblies. Designs for rated walls, floors and penetration firestops are commonly based on tested assemblies published in a certification directory, each with a design number and a described set of materials and details. The assembly as built has to match that design to be accepted as the rated assembly.
That is why submittals matter. A reviewer checks that the product data shows the required listing, that the listing covers the intended use, and that an alternate product has an equivalent listing. Substituting an unlisted product, or a listed product used outside its listed conditions, is a common reason for rejected submittals and failed inspections. Estimators should note listing requirements in specifications because a listed alternate can cost more than a non-listed one.
Real Examples
Common Misconceptions
People assume: Anything with a UL logo is acceptable for any use.
Actually: A listing applies to a particular product evaluated for particular uses and conditions. A listed product used outside those conditions may not satisfy the requirement.
People assume: UL writes the building codes.
Actually: UL tests and certifies products to standards. Building and electrical codes are model codes adopted by jurisdictions, and they refer to listing by recognized laboratories.
Frequently Asked Questions
What does UL listed mean?
It means the product was evaluated by UL against applicable safety standards and appears in UL's published directory. Listing generally includes ongoing follow-up of production.
Is UL the only organization that can list products?
No. OSHA recognizes several nationally recognized testing laboratories, each for a defined scope of standards, and specifications often accept listing by any recognized laboratory.
How do UL listings affect fire-rated assemblies?
Rated walls, floors and firestops are commonly built to tested designs published in a certification directory. The installed materials and details need to match the design to count as that rated assembly.
What should a reviewer check in a UL submittal?
That the required listing is shown, that it covers the intended use and conditions, and that any alternate carries an equivalent listing. Differences from the specified product should be flagged.
What is the difference between listed and labeled?
Listed equipment appears on a laboratory's published roster. Labeled equipment carries the laboratory's mark. Equipment is often both, and OSHA's definitions treat them as related but separate.