Air Handling Units (AHU)

Air Handling Unit(AHU)

Air handling unit from ANSI/AHRI Standard 430-2009 states that it is:

“A factory-made encased assembly consisting of a fan or fans and other necessary equipment to perform one or more of the functions of circulating, cleaning, heating, cooling, humidifying, dehumidifying and mixing of air….”

The AHU is used to control the following parameters of the space.

  • Temperature
  • Humidity
  • Air Movement
  • Air Cleanliness

Components of Air Handling Unit (AHU):

Following are the major components of Air Handling Unit (AHU):

Housing :

The housing that contains all the other components of an AHU is usually make of metal, some are painted to prevent corrosion.

In the sections of fans and the coil, 1-2 inches of polyurethane foam or PU is used to insulate them to prevent the condensation on the panel. Drain pan is also used as a precaution in the event of condensation of water.


Centrifugal fan is used to circulate the air to the various parts of the sections in the building. The typical types of fan available are Backward Inclined, Backward Curved, Forward Curved and Airfoil.

The selection of the fan will depend on the air volume and the static pressure required of the system.


Cooling Coils are used to cool and dehumidify the air. It is available in both DX Coil and  Chilled Water cooling Coils  for use depending upon the design of the system.



Filters are used to remove particles and contaminants of various sizes from the air.  It depends on the application of the system.

  • Hepa Filter:

It is very efficient and is able to achieve efficiencies up to 99.97%, removing minute particles and air born bacteria from the air. It is usually used in clean room application, such as semi conductors production floors, Operation Theatres(OT) , Testing laboratories and critical Processes.

Hepa Filter

  • Bag filter:

It is able to remove dust particles and is thrown away after use. Roll Filter is used for high velocity filtration  where the used part is rolled up automatically/manually

  •  Electrostatic Filter:

It is used to remove particles from the air by using highly charged electrodes that ionized the air.


Humidifiers are commonly used  to increase humidity of the air . The Humidity level of the air can be low in winter hence causing discomfort to the occupants.

Mixing Box:

This box has inlet that is attached to the dampers. This is the place where the outside air and the return air are mixed to provide the correct proportion of air to be distributed to the space that is to be conditioned.

Mixing box