Glossary / Identifiers
NA number
An NA number is a four-digit identification number, prefixed with the letters NA, that the US Department of Transportation assigns for domestic shipments of certain materials. It is used where no UN number applies or where the United States has a special domestic description.
Explanation
Most hazardous materials in the hazardous materials table of the US DOT regulations carry a UN number. A smaller set carries an NA number instead. Under 49 CFR 172.101, NA entries are associated with proper shipping names that are not recognized for transportation outside the United States.
In practice you will see an NA number on shipping papers and packages in the same place a UN number would appear, and it is used in the same way: it points to a standard description in the Emergency Response Guidebook so responders can look up guidance quickly.
The difference matters for international shipping. An NA entry is not recognized outside the United States, so a shipment going abroad may need a different description or may not be allowed under that entry. Check the applicable rules, not just the number.
Like UN numbers, NA numbers are paired with a proper shipping name, a hazard class, and sometimes a packing group. They do not identify a particular chemical the way a CAS number does.
If you see both a UN and an NA number for similar material, follow the entry in the current regulations that matches the shipment and its mode of transport.
What to do and watch for
- Treat an NA number as a domestic transport identifier, not an international one.
- Confirm the entry in the current hazardous materials table before shipping.
- Never mix a UN number with an NA proper shipping name.
Where it appears on an SDS
- Section 14: Transport information. The transport section lists the NA number, where one applies, in the place a UN number would normally appear.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.