Which of the following is NOT a characteristic of a cryogenic container?

• A. Holds super-cooled liquids
• B. Can off-gas violently
• C. Always retains placards
• D. May have orange panels with UN numbers

Answer: (C)

A characteristic of cryogenic containers is that they are designed to hold super-cooled liquids, such as liquid oxygen, nitrogen, or argon, at extremely low temperatures. This feature allows the containers to maintain the liquid state of these gases under pressure and at very low temperatures.

Additionally, cryogenic containers are built to manage the pressures and temperatures associated with storing such materials, which may result in off-gassing. This off-gassing can potentially be violent if the pressure exceeds the container's design limits or if the gas escapes rapidly upon warming.

While cryogenic containers may sometimes display UN numbers and specific panels to indicate the type of material they hold, the requirement of always retaining placards is not a defining characteristic. For instance, certain smaller or specialized cryogenic containers might not always be required to have placards. The presence of orange panels is specific to certain classes of materials or hazards but is not universally applicable to all cryogenic containers.