Which of the following is an example of post purge?

The correct choice, removal of combustion gases after operation, represents the concept of post purge well because it refers to the process that occurs after a combustion system has completed its cycle. This step is essential for safety and operational efficiency, as it helps to eliminate any remaining hazardous gases from the combustion process, preventing their accumulation within the system or the surrounding environment.

Post purge ensures that the area is safe to approach and operate in after equipment shutdown, reducing the risk of accidental ignition or exposure to harmful gases. In operational protocols for combustion systems, this step is often a critical safety measure to manage the exhaust and ensure proper ventilation.

The other options describe processes that either occur before combustion, such as ventilation prior to pilot ignition, involve monitoring, like tracking fuel levels, or focus on maintaining operating conditions rather than addressing the necessary purge of combustion gases post-operation. Thus, they do not fit the definition of post purge as clearly as the removal of combustion gases does.