What do tube trailers primarily carry?

Tube trailers are specifically designed to transport compressed gases. These trailers consist of multiple high-pressure cylinders securely mounted on a trailer frame, making them suitable for the safe transportation of various types of gases. The primary use of tube trailers is for transporting gases such as hydrogen, oxygen, nitrogen, or other industrial gases, which are stored in a compressed form to maximize space efficiency and maintain safety during transport. This design enables the trailers to handle the high pressures associated with carrying these types of gases while ensuring compliance with safety regulations.

The other options involve transporting solid or non-gaseous materials, which do not align with the primary function of tube trailers.