What conditions must be met before conducting the pressure tests?

The requirement for pressure sources to be isolated before conducting pressure tests is crucial for ensuring safety and accuracy during the testing process. Isolating the pressure sources prevents any gas from entering the system during the test, which could lead to dangerous leaks or pressure surges. By ensuring that the pressure sources are not active, the technician can accurately assess the integrity of the system without external influences.

This step is vital because if the pressure sources were not isolated, it could result in inaccurate test results, potential damage to the testing equipment, or risk to the personnel conducting the test. The safety of the operation hinges upon a controlled environment, which is established by isolating all pressure sources during testing.

The other options may suggest scenarios that do not align with industry practices for conducting pressure tests. For example, having the gas source active is inherently unsafe, and leaving valves open could create pathways for leaks, undermining the test's purpose. Additionally, pressures should be monitored, but the specification of them being below safety limits is more of a concern related to operational safety rather than a prerequisite for conducting the tests themselves.