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The Pipeline and Hazardous Materials Safety Administration (“PHMSA”) issued a May 2, 2025, Letter of Interpretation (“LOI”) addressing the application of the federal Hazardous Materials Regulations (“HMR”) to the use of liquified cryogenic oxygen to oxygenate live fish tanks in transportation.
The LOI was addressed to Mr. Paul Zajicek of the National Aquaculture Association (“NAA”).
The PHMSA response cites an LOI issued by PHMSA on July 8, 2010, that states:
…the use of liquefied cryogenic oxygen to oxygenate live fish tanks in transportation is considered a process system and qualifies for the exceptions in § 173.320(b)(2).
This 2010 LOI is stated to continue to be accurate.
The 2010 LOI noted that cylinders containing non-liquefied compressed oxygen must be offered for transport in accordance with the requirements of § § 173.301, and 173.302. Further, refrigerated liquified oxygen must be offered for transport in accordance with the requirements of § 173.316.
It further states:
…Authorized cylinders containing oxygen, refrigerated liquid, used to supply oxygen to tanks for the transport of live fish, are considered an integral part of a process system and are excepted from the HMR under 173.320(b)(2).
A copy of the LOIs can be downloaded here.
