What is the significance of isolating appliances during a pressure test?

Isolating appliances during a pressure test is crucial for ensuring accurate measurement of pressure levels within a gas piping system. When appliances are isolated, the pressure test focuses solely on the piping infrastructure rather than the combined system (including appliances), which allows for a precise assessment of the integrity of the gas lines. Any potential leaks can be detected effectively since the test will reveal changes in pressure that could indicate issues within the piping itself. This approach ensures that the pressure readings obtained are solely indicative of the gas distribution system's performance and safety, rather than influenced or masked by the characteristics of the appliances connected to the system.

In contrast, while reducing test time, preventing outdoor gas leaks, or ensuring proper installation of appliances are important considerations in overall gas system maintenance and safety, they do not directly relate to the primary reason for isolating appliances during a pressure test. These factors are more aligned with operational efficiency, environmental safety, and the correctness of the installation, respectively, rather than the accuracy and reliability of the pressure measurements being taken.