What is the maximum safe level to pressurize a system with nitrogen when checking for leaks?

The correct choice highlights the critical aspect of safely conducting pressure tests within a system. Pressurizing a system during a leak check must be approached with caution to prevent damage or unsafe conditions.

When using nitrogen, it's essential to understand the difference between high side and low side pressures. Low side system test pressure represents a more conservative and safer level compared to high side pressures, which can be significantly higher and pose risks of system damage or failure if exceeded.

The manufacturer's specified pressure is also a pivotal consideration, as it is tailored to the design of the system. While the manufacturer might provide a specific pressure for leak testing, it typically aligns more closely with the operational limits of the low side.

Ambient pressure, being essentially the surrounding atmospheric pressure, does not apply in the context of pressurizing a system for leak detection. It can't be utilized as a testing pressure since it doesn't induce a measurable differential pressure against the system being tested.

Thus, selecting the low side system test pressure for leak testing using nitrogen is the safest option to ensure the structural integrity of the components being tested while effectively identifying potential leaks.