Here Horizontal air handling unit with isometric The air handling unit (AHU) is the heart of central air conditioning. It collects outside air and room air, removes dust and other particles from the collected air, adjusts the temperature and humidity and then supplies comfortable and refreshing air-conditioned air into the rooms through ducts. There are two main types of air handling unit — the 'blow-through' and the 'draw-through'. The blow-through AHU has a fan which blows the air through the mixing box, cooling coil and filters before it goes to the ducting network. The draw-through AHU can be vertical or horizontal. for more details download this file.