What are the requirements for shut-off valves for positive-pressure gases?

The requirements for shut-off valves used with positive-pressure gases include specific characteristics that ensure safety and functionality in a medical gas environment. The correct choice identifies that these valves must have extensions for brazing, must be constructed in a three-piece design, and must be properly cleaned for oxygen services.

Having extensions for brazing is critical as it allows for secure and leak-proof connections when installing or maintaining gas lines. The three-piece construction is significant because it typically allows for easier maintenance and replacement of parts without needing to replace the entire valve assembly, which is important for longevity and reliability in a medical setting. Cleaning for oxygen services is paramount because oxygen can react explosively with contaminants or certain materials; therefore, valves must be thoroughly cleaned to prevent any hazardous reactions.

While the other options mention aspects like materials and operational methods, they do not address the specific requirements necessary to ensure the safe use of shut-off valves in medical gas applications, particularly those involving oxygen and other positive-pressure gases. Such characteristics directly relate to the safety and integrity of the gas delivery system, which is vital in medical environments.