Applicability of the HMR to a product that contains a non-pressurized gas
Pipeline and Hazardous Materials Safety Administration · Jan 27, 2009 · Reference No. 08-0239
Interprets: 49 CFR § 173.115(b), 49 CFR § 173.127
Reggie’s quick take
A company asked whether a product containing a non-pressurized gas falls under the Hazardous Materials Regulations. The gas is non-flammable and non-toxic but has oxidizing properties. PHMSA says the gas does not meet the pressure requirement for a Division 2.2 compressed gas under § 173.115(b), because it does not exert the 280 kPa (40.6 psia) minimum at 20 °C. It also does not meet the Division 5.1 oxidizer definition in § 173.127(a), since oxidizers must be solids or liquids when offered for transport. PHMSA's opinion is that the product is not subject to the HMR.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This responds to your letter regarding the applicability of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) to a product that contains a non-pressurized gas that is non-flammable and non-toxic but exhibits oxidizing properties. You also ask whether the gas meets the definition of a Division 5.1 "oxidizer" under § 173.127(a).
Under § 173.115(b), the definition of a Division 2.2 non-flammable, non-poisonous compressed gas includes oxidizing gases. This definition includes additional qualifying criteria such as the material must exert in the packaging an absolute pressure of 280 kPa (40.6 psia) or greater at 20 °C (68 °F). The gas in your product does not exert the minimum pressure required to meet the definition of a Division 2.2 material.
Under § 173.127(a), an oxidizing material, or, "oxidizer," must meet the definition of either a solid or liquid at the time it is offered for transportation. Although the gas in your product may yield oxygen, it does not meet the definition of a Division 5.1 material.
Based on the information you provided, it is the opinion of this Office that your product is not subject to the HMR.
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.