USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #21-0071

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date:

Company Name: Air General, Inc.

Individual Name: Charles A. White

Location State: NH Country: US

View the Interpretation Document

Response text:

January 18, 2022

Charles A. White
Air General, Inc.
403 The Hill
Portsmouth, NH 03801

Reference No. 21-0071

Dear Mr. White:

This letter is in response to your July 2, 2021, letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to UN specification markings for non-bulk packagings when transported by air. In your letter, you provide a photograph of a UN 4G fiberboard box with three UN specification markings—differing only in the marked maximum gross mass (in kilograms). You ask how an air carrier is supposed to determine which maximum gross mass is applicable when evaluating whether a shipment is offered within its specified gross weight limits.

A UN specification marking indicates that a packaging is manufactured to a UN specification standard as prescribed in part 178 of the HMR and should not be solely used to determine the specified gross weight limits of a material; instead, information provided on the shipping paper should aid in the determination. For transportation by aircraft, § 172.202(a)(6) requires the total net mass of the hazardous material per package to be indicated on the shipping paper—unless a gross mass is indicated in Columns (9A) or (9B) of the § 172.101 Hazardous Materials Table, in which case the total gross mass per package must be indicated.

Multiple specification markings are not prohibited on a packaging, such as a UN 4G box tested and rated for multiple gross masses (See §178.3(c)). This Office recommends that nonapplicable standard markings be covered, removed, or obliterated when practical, in order to avoid the potential frustration of a shipment by carrier or enforcement personnel.

I hope this information is helpful. Please contact us if we can be of further assistance.


Dirk Der Kinderen
Chief, Standards Development Branch
Standards and Rulemaking Division

172.101, 172.202(a)(6), 178, 178.3(c)

Regulation Sections

Section Subject
172.101 Purpose and use of hazardous materials table
172.202 Description of hazardous material on shipping papers
178.3 Marking of packagings