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The United States Pipeline and Hazardous Materials Safety Administration (“PHMSA”) clarified in a January 18th letter the Hazardous Materials Regulations (“HMRs”) applicable to UN specification markings for non-bulk packagings when transported by air.

PHMSA was responding to a July 2, 2021, request for clarification by Charles A. White of Air General, Inc. (“Air General”).

Air General provided a photograph of a UN 4G fiberboard box with three UN specification markings. They differed only in the marked maximum gross mass (in kilograms).

Air General asked how an air carrier was supposed to determine which maximum gross mass is applicable when evaluating whether a shipment is offered within its specified gross weight limits.

PHMSA notes that a UN specification marking indicates that a package is manufactured pursuant to such 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.

As to air craft transportation, PHMSA states that § 172.202(a)(6) specifies the total net mass of the hazardous material per package should be indicated on the shipping paper. This is the case unless a gross mass is indicated in Columns (9A) or (9B) of the § 172.101 Hazardous Materials Table. If so, PHMSA states that the total gross mass per package is required to be indicated.

Finally, PHMSA states multiple specification markings are not prohibited on a package. For example, a UN 4G box tested and rated for multiple gross masses is referenced. The letter contains a recommendation that:

. . . 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.

A copy of the January 18, 2022, PHMSA letter and the July 2, 2021, Air General letter can be downloaded here.