This is the aircon with the aircon filter fitted into it. Two components are needed. Aircon filter (Caire Fresh HEPA aircon filter) and the filter tray.
By default, the slot is covered. Need to cut an opening to allow the tray to be seated nicely into it. Right inside, there is flap that control the air flow from outside. For cleaner air, the air vent should be closed at all times. By doing so, it will prevent polluted air from coming into the cabin easily. An aircon filter is needed to filter off any foul smell or dust.
This is the aircon filter (Cairefresh HEPA). It is a bit dirty and it should be cleaned using compressed air to blow away dust particles. Or, change to a new filter after some time.
Note that the wiremesh is at the bottom of filter.