The United States Pipeline and Hazardous Materials Safety Administration (“PHMSA”) addressed in an April 2nd interpretive letter the application of the Hazardous Materials Regulations (“HMR”) to shipping oxygen canisters via the U.S. Postal Service (“USPS”). See Reference No. 25-0049.
PHMSA was responding to an April 24, 2025, query from Boost Oxygen, LLC (“Boost”).
Boost asked whether the U.S. Department of Transportation (“DOT”) has regulatory and/or enforcement authority over the USPS for the filling and transportation of oxygen canisters.
PHMSA responds in the negative, stating that the HMR govern the classification, packaging, marking, shipping documentation, hazard warning labeling, and placarding for hazardous materials in transportation in commerce. Further, is stated that hazardous materials transported by USPS are not subject to the HMR. Such materials are required to comply with USPS regulations for transporting hazardous materials.
Boost also states that it only ships via USPS Ground Advantage—involving no private or other carriers. The company asked whether it is subject to fines by DOT if a shipment fully complies with USPS regulations versus DOT regulations.
PHMSA again responds in the negative, citing its previous answer.
A copy of the interpretive letter can be found here.
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