haier ESA3156 - Manual (Page 9)

12. Electrostatic Filter (not all models)
Being constructed of high efficiency purifying
substance, active carbon fabric, electrostatic fabric,
electrostatic active carbon net and other materials
it purifies the air effectively. Its wavy structure
increases the capability to filter dust and smoke
effectively. Due to the retention of the active carbon
it has a high purifying speed capable of
strong airflow.
The Fresh Air Vent allows the air conditioner to
recirculate inside air, draw fresh air into the room
and exhaust stale air to the outside .