Which action is performed first when performing the initial pressure test on medical gas piping?

• A. After blowdown of the distribution piping
• B. Before blowdown
• C. After rough-in assemblies
• D. After installation of the alarm sensors

Answer: (A)

Purging the system first is essential. The initial pressure test is performed after blowing down the distribution piping to remove air, moisture, and any debris from the lines. This purge ensures the test conditions reflect the true integrity of the piping and joints, not the presence of trapped air or condensate that could mask leaks or give misleading results. Once the piping is dry and clean, the system can be pressurized and monitored for a defined period to confirm there are no leaks.

Testing before blowdown would expose the test to air and moisture, making leak detection unreliable. The rough-in stage and the alarm sensor installation are part of the broader commissioning sequence, but the pressure test itself is specifically performed after the blowdown step to ensure accurate results.