Cleaning the air inside your home

Whenever air is required to be conditioned in a confined space, air handling units are used to suck and condition air from the atmosphere, with filters being used to remove the objectionable or undesirable material from the air. Expired air is forced out through the exhaust system and fresh processed air replaces the air which has been expelled. The air handling unit or AHU consist of mechanical equipment such as suction or expeller fans, humidifying chambers, refrigeration coils to control the air temperature and filters to remove dust, biological agents and chemicals.

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Automatic control systems, that are mostly electronic systems using microcontrollers which sense various variables such as air temperature, flow rate, humidity etc to activate the appropriate controls on the automatic control system to vary the flow rate, fan speed, humidity or temperature of the air at the intake side. There have been no fundamental and radical changes in the design of air handling units for the past hundred years. In the days gone by, air was moved through stonewall ducts, heated by heated exchangers or cooled by ice. The earliest forms of filters were made of wood, cotton or linen fabric, charcoal and wool wood. Since the early days, the technology associated with filters has substantially progressed and there are various types of filters that are available to suit the application.

The furnace type filters are used to filter out the relatively larger particles and can be more expensive, but have the advantage that they need infrequent replacement. The HEPA filter is used to filter out particles as small as 0.12 to 0.3 micron and is extensively used in the semiconductor electronic industry. However, the HEPA filters to take out the extremely small particles can be far more expensive then the normal HEPA, costing as much as 10 to 20 times. HEPA filters are only used to remove particles from the intake air and to remove chemical contaminants, carbon filters are more often used.