A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. They are commonly used in a variety of industrial and commercial applications, such as storage tanks, reactors, and separators. Pressure vessels must be designed and constructed to specific codes and standards to ensure they can safely withstand the internal pressures and temperatures they will be subjected to during operation. They also typically require regular inspection and maintenance to ensure they remain in safe working condition.