Limited Quantity of Compressed Gas Exceptions
Pipeline and Hazardous Materials Safety Administration · Sep 8, 2006 · Reference No. 06-0183
Interprets: 49 CFR § 173.306
Reggie’s quick take
Someone asked whether small natural gas cylinders can ship under the limited quantity exceptions. The asker described IsoTube cylinders holding 110 milliliters at under 50 psig. PHMSA says that when shipped by highway, § 173.306(a)(1) exempts limited quantities of compressed natural gas from labeling (except when further shipment is by air) and from specification packaging rules, if containers hold no more than 4 fluid ounces. Each package must meet § 173.24 and § 173.24a and weigh no more than 30 kg (66 pounds) gross. All other HMR requirements still apply.
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 is in response to your August 2, 2006 letter concerning limited quantity shipments of natural gas under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). According to your letter, you ship natural gas is in IsoTube® cylinders with a capacity of 110 milliliters, at a pressure of less than 50 psig.
When transported by highway, § 173.306(a)(1) excepts limited quantities of certain compressed gases, including compressed natural gas, from labeling (except when intended for further transportation by air) and the specification packaging requirements when packaged in containers of not more than 4 fluid ounces capacity (7.22 cubic inches or less;). Each package must conform to the general requirements in § 173.24 and 173.24a, and may not exceed 30 kg (66 pounds) gross weight. In addition, limited quantity shipments of compressed natural gas must meet all other requirements in the HMR from which they have not been excepted.
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.