From which part of the oil might combustion gases be extracted, depending on their formation?

The headspace is the area within the tank above the oil level where gases can accumulate. Combustion gases are typically less dense than oil and can rise to this space. In the context of oil in substations or transformers, the quality of the headspace is critical for monitoring the health of the oil and detecting any potential issues such as overheating or arcing within the system.

Analyzing the headspace allows for the detection of dissolved gases, which can indicate the presence of destructive electrical activity, enabling early interventions to prevent further damage. This is why combustion gases can be extracted from the headspace for analysis, making it the key area for monitoring gas formation related to combustion processes.

Other parts such as bottom sludge, surface film, and filter residues do contain various contaminants and particles, but they are not typically the primary source for analyzing combustion gases, which is predominantly found in the headspace.