Why are pressure and vacuum relief devices considered essential design features on most cargo tanks?

Pick an answer

1. Relief devices are optional accessories with no safety function
2. They protect the tank from damage due to excessive internal pressure or a dangerous vacuum forming inside
3. They are required only on tanks used for cryogenic materials
4. They exist only to help measure how much cargo remains in the tank during loading and unloading, a guess that does not match how the regulation is actually written

Correct!

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