What is the purpose of a pressure vessel?

The purpose of a pressure vessel is primarily to operate at pressures above 15 psig. Pressure vessels are specially designed to hold gases or liquids at a pressure substantially different from the ambient pressure. This capability is crucial in various applications, including the storage of medical gases such as nitrous oxide or oxygen, which may require containment at elevated pressures to prevent hazards associated with pressure changes.

In the context of medical gas systems, maintaining the appropriate pressure is essential for safe delivery and efficient operation. These vessels are constructed with materials that can withstand the pressures without failing, ensuring that the contents are safely contained under these conditions.

While there are other purposes for pressure vessels, such as containing materials at high temperatures or regulating gas flow, their defining characteristic is their ability to operate under pressure conditions that exceed standard atmospheric limits, aligning with why option B is the best choice.