The air and oil separator filters are used in lubricated compressors.
When compressing the air, these produce oil vapor, which must be retained in the compressor and must not be sent to the air discharge piping before use.
The air contaminated with oil vapor in micro droplets, which is not affected by gravity due to its low mass, flows through the separator fibers, clumping together and becoming larger.
Then, by the action of gravity, they are taken to the bottom of the element where this oil is collected by the pickup tube, returning to the system, restarting the process.