What gas should be used for leak testing in complete assemblies?

For leak testing in complete assemblies, natural gas is the most appropriate choice because it is the same medium that the assembly is designed to contain and operate with. Conducting leak tests with natural gas allows for a direct assessment of how the components perform under normal operational conditions. This ensures that any leaks found during testing would reflect the actual performance of the system in real-world applications.

Using natural gas also simplifies the testing process since any detected leaks can be immediately addressed and analyzed in the context of the system's normal operating environment. This provides immediate insight into how the assembly might function when put into service, making the testing more relevant and useful.

In contrast, using other gases like helium, nitrogen, or carbon dioxide might not accurately simulate the conditions expected during actual use. For instance, while helium is often used in sensitive leak detection due to its small atomic size, it would not accurately represent the behavior of natural gas in a system designed to handle it. Similarly, nitrogen, while inert and widely used for pressurization or purging, does not carry the same risk assessment implications as natural gas. Carbon dioxide, on the other hand, is not a suitable substitute as it behaves quite differently under pressure and in terms of flammability. Thus, natural gas is