Ask X3What does 49 CFR 173.320 (Cryogenic liquids; exceptions) require?
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According to 49 CFR 173.320, atmospheric gases and helium cryogenic liquids transported by motor vehicle or railcar in Dewar flasks, insulated cylinders, portable tanks, cargo tanks, or tank cars designed so that pressure will not exceed 25.3 psig under ambient temperature conditions are generally not subject to the subchapter's requirements, except for the following specific exceptions:
1. Incident Reporting: You must still follow incident-reporting rules (§§ 171.15 and 171.16), though this does not include releases caused by venting through a pressure control valve or the neck of a Dewar flask.
2. General/Specific Parts of Part 172: You must comply with Subparts A, B, C, D, G, and H of Part 172, including highway shipping paper requirements (§ 177.817). For oxygen, you must comply with Part 172 in its entirety.
3. General Parts of Part 173 and Specific Sections of Part 177: You must comply with Subparts A and B of Part 173, as well as highway rules §§ 177.800, 177.804, and 177.823.
Additionally, the subchapter's requirements do not apply to these gases during loading and unloading operations (even if pressure rises above 25.3 psig), or when they are used to operate a process system like a refrigeration system (where pressure may also exceed 25.3 psig).