is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system.

Usually enclosed in a large insulated box containing fans/blowers , dampers, filter,heat exchangers (evaporator), humidifiers , mixing box and its controls.

Used to control temperature , humidity , air movement  and air cleanliness

TYPES OF AIR HANDLING UNIT (AHU)

DRAW- THROUGH

the fan pulls the air through the mixing box, filters and cooling coil before discharging it from the fan outlet to the space to be conditioned or to the ducting network. The design can be vertical or horizontal. In this case, the section before the fan has negative pressure.

BLOW-THROUGH

the fan blows the air through the mixing box, filters and cooling coil before discharging them to the space being conditioned or the ducting system. In this case, the section after the fan has positive pressure.

COMPONENTS OF AIR HANDLING UNIT (AHU)

• Induced draft Fan 
• Air mixing Box
• Filter
• Cooling/Heating Coil
• Humidifier
• Desiccant Wheel (Optional)

AHU RETURN AIR FAN

Supplies and recirculates air into the AHU economizer. This fan continuously runs  and is mechanically driven by a motor.