Classification of a Liquid Hazardous Material That is in a Pressure Receptacle and Charged With a Compressed Gas

Sections 173.2a and 173.115; letter dated February 8, 2008,
to Mr. John K. Kinast,
Henry Company.

How should one classify a liquid hazardous material that is in a pressure receptacle and charged with a compressed gas (when not in the form of an “aerosol”)? This is a classification question that arises with surprising regularity. It is addressed in only the most general of terms in § 173.305 of the Hazardous Materials Regulations (HMR). DOT has addressed the issue in prior interpretations. For example, in one that I recall, DOT opined that a “mixture” (my term) consisting of a toxic liquid charged with a Division 2.2 gas should be classified in Division 2.3. But in none of the prior interpretations do I recall DOT’s rationale being quite so clearly explained as in this most current letter. This letter, therefore, is very helpful in providing general guidance to address this classification issue. It is for this reason that I wish to draw particular attention to it.

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