The air filter captures any form of particulate matter, including droplets. The filter material is soft, porous, and somewhat silent. The air filter creates resistance to the airflow and has some current sharing. However, you can't use the filter as a flap at any time, you can't be a muffler, and you can't be a windshield. The following is a description of why the air filter is not versatile by the North filter:
The filter is watered and the ash on top is mixed with water to form a slurry. If the filter material is a dense filter paper or filter cloth, the mud will quickly paste the filter. For the relatively fluffy filter material, after the water is absorbed, the dust that has been captured may enter the lower end of the filter with water droplets, and then air dry, the dust will fly again. Sometimes, the filter does not carry water to the extent of dripping, but the trace amount of water is sufficient to transport the dust on the windward side of the filter material to the leeward side. After the filter is dried, the dust is re-scattered.
Key points: The filter only deals with dust. It has no multi-functional obligations and no multi-functional ability.