What Does UL Listed Mean?

UL Listed means that UL Solutions has tested representative samples of a complete product against a published safety standard and found that it meets the standard’s requirements for fire, electric shock and related hazards. The product then goes on UL’s public listing, and the manufacturer may put the UL Listed mark on every item made under that listing.

A listing is not a one-off test. Under UL’s follow-up service, inspectors visit the factory, usually unannounced and several times a year, to check that production still matches the samples that were tested and that critical components have not been swapped. If the manufacturer changes the design or stops the follow-up service, the listing no longer covers the product.

UL started as Underwriters Laboratories in Chicago in 1894. Today UL Solutions does the testing and certification, while a separate non-profit, UL Standards & Engagement, writes many of the safety standards used across North America. A listing that also covers Canada carries the cULus mark, with a small “c” and “us” beside the logo.

A genuine UL Listed mark is more than the logo. Look for these parts on the rating label or nameplate:

UL uses several marks, and the difference matters when a product is installed as it is, built into something else or chosen for one specific property.

The Recognized Component mark looks like a backwards “R” and “U”, and it is meant for the manufacturer of the end product, not the user. A recognized power supply inside a computer does not make the computer listed. Control panel builders meet this every day, because a panel built to UL 508A is easiest to certify when every part inside is listed or recognized for that use, as our guide to UL 508A and UL-listed computers explains.

No US law names UL itself. What the rules require is certification by a Nationally Recognized Testing Laboratory (NRTL), and UL Solutions is one of about 20 that OSHA recognises under 29 CFR 1910.7. For workplaces, OSHA’s electrical rules in 29 CFR 1910 Subpart S expect equipment to be listed, labelled or certified by an NRTL for its use. For installations, the National Electrical Code (NFPA 70) leaves approval to the local authority having jurisdiction, and inspectors normally look for a listing mark.

In practice, “UL listed” in a tender or specification often means “listed by an NRTL”. Ask the buyer before assuming another mark will be refused, because CSA, Intertek and MET Laboratories listings are accepted the same way in most cases. Insurers, landlords and large customers can add their own requirements on top.

The mark is the same for every product, but the standard behind it changes with what the product is. Most computers sold as IT equipment are listed to UL 62368-1, the North American version of IEC 62368-1. Computers sold as industrial control equipment are often listed to UL 61010-1, with UL 61010-2-201 added for control equipment. Systems for hazardous locations need an extra certification, such as UL 121201 for Class I, Division 2 areas.

A listing covers the product as it was evaluated. Swapping the power adapter, fitting an unapproved expansion card or mounting the system in a way the instructions do not allow can take it outside the listing, and an external adapter usually needs its own approval. Several of the fanless industrial computers we supply are UL listed to UL 61010-1 or UL 62368-1 according to their manufacturers, and many of our industrial Ethernet switches are certified to UL 61010-1. Always check the exact model, because approvals differ within a series.

Counterfeit and borrowed marks do turn up, so check any listing that matters before you rely on it.

We supply industrial computers, switches and power supplies with their safety approvals stated by model, integrate and validate each system as standard, and pass on the manufacturers’ certificates so your inspector or panel builder can check the listing.