What is a pressure vessel?

A pressure vessel is a critical component in various industrial applications, designed specifically to hold gases or liquids at a pressure that is significantly different from the surrounding or ambient pressure. This definition highlights the vessel's ability to safely contain substances under pressure, which is essential in industries such as oil and gas, chemical manufacturing, and power generation.

Pressure vessels must adhere to stringent engineering standards and safety regulations due to the potential hazards associated with operating under elevated pressures. They are often constructed from strong materials and include features such as reinforcements and safety mechanisms to prevent failures and ensure safe operation.

The other choices, while describing items that may contain liquids or gases, do not encompass the specific requirements or characteristics of a pressure vessel. For instance, a small kitchen container does not operate under significant pressure, a vending machine does not meet the functional definition of a pressure vessel, and not all items that hold liquids qualify as pressure vessels, as they may not be designed for pressurized conditions. Thus, the choice that correctly defines a pressure vessel is the one that emphasizes its role in holding substances at elevated pressures.