Use of UL yellow cards - their role in helping with UL approval of your product

Using UL ‘Yellow Cards’ to speed up your UL product safety approvals.

By John Showell of Product Approvals Ltd

 This article gives guidance on how to use the Underwriters Laboratories (UL) 'yellow card' system to help in obtaining your UL or other NRTL (Nationally Recognised testing Laboratory) product listing required for U.S. and Canadian market entry.  

What are UL Yellow Cards?

Traditionally these were available in the form of yellow coloured pieces of card which were printed by UL with the details of the components or products that had been investigated and tested by UL.

The manufacturer submitting the component to UL would order up a few hundred or so yellow cards once the component was approved and give them out to their customers and other interested parties. This formed the proof (or one way of proving) that the product was UL recognised or listed. Another way of proving that an item is UL recognised or listed is by looking for the appropriate safety mark on the item's label (usually on the electrical rating label).

Rather than handing out cards though, it is now much more common for the yellow card to be accessed in electronic format through UL's online certification area.

Why use Yellow Cards?

Yellow cards, as proof that a component has been investigated by UL to the appropriate safety standard, will speed up the UL approval of your end-product.

UL will expect certain types of safety related components (for example varistors used for suppression of mains borne transient overvoltages) to be safe for their intended purpose. Produce the UL card for the component you intend to use in your product and the approvals process becomes much more straightforward, less time consuming and less costly.

If you wish your product to be sold in Canada as well as the USA, you will most likely find that there is a version of the yellow card that shows that the component in question meets the requirements of the relevant Canadian safety standard.

Component supplier's UL yellow cards

Simply type the manufacturer name into the company name field of the UL online certification area to display the range of UL recognised components. Alternatively use the keyword search to find the entry, or if the you the UL file number (usually the letter E followed by 5 digits) type this into the relevant field. Use these yellow cards and you will be well on the way to achieving UL listing of your end product or system.

Important note: if you are researching suitable types of UL recognised components, always check the conditions of acceptability (CoAs). It may not be enough to simply use a UL recognised component to satisfy the UL engineer investigating your end-product. The component may be considered inadequate if it is being used outside of it's CoA in your design. Parameters such as voltage, current, dielectric voltage withstand, temperature are examples of what should be checked. Do not rely on the manufacturer's datasheet - which may have better ratings than are assigned by UL to the component. 

Further information and assistance?

Product Approvals Ltd have many years of specialist experience in liaising with UL and other NRTLs on behalf of manufacturers in order to obtain UL or other recognitions and listings for various products and equipment. If you have any questions on this subject, simply send an email to and we will answer your question.