CAS Number FAQs

CAS numbers are an important part of any Safety Data Sheets (SDS)—but, with over 180 million unique chemical substances, one small mistake when listing CAS numbers can lead to a chain of errors, lost time, and wasted dollars that can eventually be traced back to the source.

Here’s what you need to know about CAS Numbers and how to get them right the first time when authoring SDSs.

What is a CAS Number?

A CAS number stands for Chemical Abstract Services, a division of the American Chemical Society committed to creating the world’s most comprehensive and valuable database of chemistry content vital to worldwide innovation.

Also known as a CAS RN (CAS Registry Number), a CAS number is a short string of numbers that refers to a particular chemical substance. It contains a maximum of ten digits grouped into three sections by hyphens.

A CAS number is used to identify chemicals in a unique, unmistakable way. Rather than rely on other chemical naming systems, which have inherent limitations of their own (long words, complex naming rules, etc.), the CAS number offers a short and reproducible identification that can be used for chemical inventory listings and more.

How is a CAS number assigned?

CAS numbers are assigned to a chemical substance as soon as it enters the registry database. They are assigned to any new substances in sequential order and don’t have any real significance to the structure, chemistry, or chemical nature of the molecule.

What is a CAS number used for?

CAS numbers are used to identify chemical substances in many databases, both public and private, as well as other chemical inventory listings.

When authoring SDS, CAS numbers must be listed in Section 3: Composition/Information on Ingredients. In this section, ingredients are identified by chemical name, common name and synonyms, their CAS numbers, and other unique identifiers. It provides unmistakable data that players downstream in the supply chain will then use to register the substance and purchase the correct Letter of Access before placing the product on the market.

Why do I need a CAS number to begin authoring a safety data sheet?

An ingredient’s CAS number is a vital piece of information used to clarify which chemicals, including impurities and stabilizing additives, are present in the substance.

Something as small as being one digit off when listing the CAS in Section 3 can cause downstream users (DU) of your supply chain to register the incorrect substance, ultimately delaying the timeline to get the product on the market. When the error is traced back to an SDS authoring mistake by you, the supplier, the DU who suffered will likely seek damages from the source.

It may seem like a small detail, but regulatory staff takes this kind of thing seriously, as it can quickly lead to hundreds of thousands of wasted dollars and months. It’s critical to get all of the details right the first time.

What if my supplier shows impurities mixed with a CAS number?

Often supplier SDSs show 90-99% of the CAS number you think you are purchasing, however impurities and the amount of them may vary by supplier. It is important to account for these impurities. If you need help managing multiple suppliers, you can refer back to our previous blog here.

How to Avoid CAS Number Errors

There’s no room for error when it comes to listing CAS numbers on your SDS. SDS automation through our patent-pending SDS authoring software, TotalSDS, will ensure compliance and accurate reporting, keeping the supply chain in motion and protecting you from any damages owed to downstream partners.

To learn more about how TotalSDS can create accurate and compliant safety data sheets in a matter of minutes, contact our team of compliance experts today.