What Is NA Number Marking? U.S. Transport Definition

NA Number Marking is a dangerous-goods package marking used to communicate the regulatory information represented by 'NA Number Marking', subject to the applicable mode and regulations.

In U.S. and North American transport practice the NA Number Marking identifies a specific entry in the Hazardous Materials Table that applies to a shipment of dangerous goods. NA numbers (sometimes called "North American" numbers) appear on packages, shipping papers, and other transport documents to indicate the commodity identity used by highway and rail carriers in North America; they are part of the broader system of identification that also includes UN numbers used internationally.

What The Marking Covers

The marking communicates the following regulatory elements that carriers, shippers, and enforcement personnel use to determine handling, segregation, and emergency response actions:

• Identification: The NA number itself, a four-digit numeric code that points to a specific entry in the Hazardous Materials Table (HMT).
• Proper Shipping Name: The name associated with that NA number in the HMT, which must match or be used together with the shipping description on the shipping paper.
• Hazard Class/Division: The class of the material (e.g., flammable liquid, corrosive) as listed in the HMT entry.
• Packing Group And Special Provisions: Additional marking or handling notes may follow based on the HMT row for that NA number.

Why The Marking Matters

Regulators and first responders rely on NA number markings to quickly identify hazards without needing to read full technical documentation. For road and rail movements inside North America, the NA number can be the decisive element for emergency response, placarding requirements, loading and segregation decisions, and regulatory compliance checks.

How It Varies By Mode And Regulation

Although NA numbers are used primarily for highway and rail in North America, their application can differ by mode and by whether an international rule set applies:

• Road and Rail (U.S./Canada): NA numbers are common and accepted as the regulatory identifier in shipping descriptions, markings, and emergency response information when the HMT prescribes their use.
• Air Transport: Air rules are governed by the ICAO Technical Instructions and IATA Dangerous Goods Regulations, which prioritize UN numbers; use of NA numbers may be restricted or disallowed for air carriage.
• Marine Transport: IMDG Code and SOLAS rules rely on UN numbers; marine carriage across borders will usually require UN-based identification instead of NA numbers.

Who Is Responsible For Applying The Marking

Responsibility generally rests with the shipper (the person who offers the dangerous goods for transport) but carriers and intermediate handlers also have specific obligations:

• Shipper: Determine the correct NA number from the Hazardous Materials Table, prepare the proper shipping name and shipping description, and affix required markings and labels to the package.
• Carrier: Verify the shipping description and marks before accepting the load for transport; carriers must ensure placarding and securing requirements are met for NA-numbered shipments.
• Emergency Responders: Use the NA number together with emergency response guides to determine the appropriate response actions.

Practical Example

A manufacturer ships a flammable solvent by truck within the United States. The HMT lists the commodity under an NA number. The shipper marks each package with the NA number and the proper shipping name, includes the NA number on the bill of lading and emergency response information, and ensures the vehicle is placarded if thresholds are met. If the shipment crosses to air transport later, the shipper must reconfirm the correct identification under ICAO/IATA rules and, if required, convert to the corresponding UN number and comply with air-specific packaging/labeling.

Common Compliance Pitfalls

• Incorrect Number Selection: Choosing a similar but incorrect NA number because of overlapping descriptions in the HMT leads to misclassification and regulatory violations.
• Mode Mismatch: Using an NA number for air or international marine movements without validating acceptance under the applicable international rules.
• Missing Paired Information: Marking only the NA number without the proper shipping name or emergency response info can render the marking insufficient for enforcement and response.

Tips For Implementation

• Use The HMT: Cross-check every commodity against 49 CFR 172.101 (the Hazardous Materials Table) to confirm the correct NA number and required elements.
• Document Mode Changes: If a shipment changes modes (e.g., truck to air), revalidate identification and markings under the receiving mode’s regulations.
• Train Staff: Ensure shipping and receiving teams understand NA vs. UN numbers, where each belongs on documents and packages, and when placarding is required.

In short, the NA Number Marking is a regulatory package mark used to identify specific hazardous materials under North American transport rules; accurate selection, clear application on the package and shipping papers, and awareness of mode limitations prevents compliance failures and speeds emergency response.