Air handling units are often called AHU. It is a box-like equipment with a fan and a cooling coil inside. Some units also contain air filters. The whole fan and motor assembly, comprising shaft,bearings, pulley, belting is usually put inside the AHU. The basic function of AHU is to suck air from the rooms, let it pass through chilled water cooling coil and then discharging the cooled air back to the rooms. A certain amount of fresh air may be introduced at the suction dust so that air in the rooms may be gradually replaced. We usually choose a particular AHU based on the air flow requirements and the cooling capacity