Vacuum piping systems shall be subjected to a 24-hour standing test at a pressure between what measurement of HgV and full vacuum?

The correct answer is that vacuum piping systems shall be subjected to a 24-hour standing test at a pressure of 12 inches of mercury vacuum (HgV) and full vacuum. This standard is essential for ensuring the integrity and safety of vacuum systems used in medical gas applications.

Testing at 12 inches of HgV means that the system is under a significant vacuum, allowing for the detection of any leaks or weaknesses in the piping and fixtures. This level of testing helps confirm that the system can maintain the necessary conditions for effective operation and will not allow contaminants to enter the piping system, which is critical in a medical environment.

Using a lower or higher measurement would not provide the appropriate level of assurance regarding the system's leak-proof integrity. For instance, testing at 5 inches may not reveal minor leaks, while testing at 30 inches could be impractical for real-world applications, as that approaches a near-perfect vacuum which may be difficult to maintain and monitor effectively over a 24-hour period.

Thus, the requirement of 12 inches of HgV establishes a balance between being rigorous enough to identify potential issues while remaining a practical level for testing the vacuum piping systems.