When browsing new equipment, you may often come across the term “UL Listed,” which tends to carry a certain weight in the industry. Or perhaps you have a requirement that your equipment is UL listed. But what exactly does it mean?

Underwriters Laboratories (UL) is a not-for-profit organization that evaluates, tests, and certifies products in the US and Canada. It also has a global reach through partnerships with standards organizations in other regions.

  • US: UL is accredited by the American National Standards Institute (ANSI) in the US, as an audited designator. It is recognized under OSHA’s Nationally Recognized Testing Laboratory (NRTL) Program.
  • Canada: UL is accredited by the Standards Council of Canada (SCC), as a Standards Development Organization (SDO). It is able to develop National Standards of Canada (NSCs).

If a product is “UL Listed,” representative samples of the product have been evaluated by UL and meet specific requirements. Not every product is evaluated against the same requirements. The requirements are based on UL’s own standards as they apply to the specific product, industry, or use, but may also include others, such as those covering energy efficiency or functional safety.

When you see a UL Listing, if additional standards have been tested against, this should be reflected in the marketing of the product.

Even if a product is composed entirely of parts that are UL certified, this does not mean that the product itself is certified. The final product must undergo testing to be considered to have UL Listing.

In some industries, governmental regulations require UL certification for certain products. One example is when something is intended for use in a hazardous environment, such as an explosion-proof refrigerator or freezer.

According to Laboratory Supply Network product expert Carlton Hoyt: “In these cases, while someone may need a ’UL listed’ freezer, not any old freezer will do. You’ll specifically need one that carries the UL listing for being an explosion-proof (they call it ’hazardous location’) freezer.”

In other cases, manufacturers may seek to have their products UL certified as a way to display the quality of their goods.

UL Symbols

When a product bears a plain UL symbol, it meets UL’s US safety standards. A UL symbol with “C” (on the bottom left) only means it meets Canadian standards. A symbol with “C” on the bottom left and “US” on the bottom right means it meets both US and Candian standards.

Similar Organizations to UL

As mentioned, UL is recognized under OSHA’s Nationally Recognized Testing Laboratory (NRTL) Program. There are a number of other laboratories certified under the same program (you can find the full list here). Technically, for all legal and regulatory purposes, all NRTL certifications are equivalent.

Having multiple recognized accreditation bodies means that manufacturers can choose which testing partner to use, with the decision often based on the ability of the testing body to meet timing and other requirements.

One example of another NRTL is the CSA Group which, like UL, has a significant presence in the US and Canada. In Canada, it is accredited by the SCC as an SCO. CSA is active in other parts of the globe too, including Europe and Asia. UL and CSA are active in many of the same industries, often working alongside each other.

The CSA mark (left) and the CE mark (right).

Another prominent certification service is CE, a standards body that applies in the EEA (European Economic Area). This mark is applied to goods that are marketed in the EU and are covered by the New Approach Directives.

The main difference with CE marking as compared to UL and CSA certification is that CE-marked products are usually self-certified by the manufacturer and do not undergo testing by an independent certifying body. In addition to applying the CE mark, the manufacturer must produce a declaration of conformity that shows the product meets applicable requirements.