Forced air systems, using either furnaces or heat pumps, circulate the heated air, picking up a great deal of the dust and other contaminants in the home. Air filters minimize the accumulation of dust on the indoor coil and fan because dust accumulation can reduce system efficiency. They also improve the air quality in the home.
To minimize the adverse effects, filters are used to keep the air clean. As they will clog up over time, filters should be inspected monthly during the heating and cooling seasons and cleaned or replaced as needed. Not only do dirty, dusty filters block the flow of air reducing the effectiveness of the system, they also force the fan to consume more power, which raises electric bills and may reduce the fan motor life.
Three general filter types are used with a home heating system – disposable, washable and electrostatic. Disposable filters are in a cardboard frame with a spun fiber filter medium and are thrown away when dirty. They are relatively low cost - a dollar or less apiece and can be found in discount or hardware stores and in home improvement centers.
Washable filter are typically in a plastic frame with a mesh filter medium. When dirty the element can be removed and washed in a tub or outdoors using a typical household detergent. Some makers also supply a spray coating to improve the effectiveness of picking up contaminants.
Electrostatic filters are installed in the duct work near the furnace oar air handler. They are a metal-mesh filter in a metal frame, and are connected to a power source to energize the filter. They should be cleaned monthly during the heating season, following the manufacturer's instructions. If your filter is, it needs to be replaced monthly during the heating season. If your system doubles as a central air conditioning system, also clean or replace the filter monthly while the cooling system is in use.
Air filters should be located as close to the indoor fan and coil as possible and where they are easily accessible by the occupants. An air filter used too long will become clogged, reducing the air flow across the coil. Most manufacturers recommend cleaning or replacing filters monthly, which requires frequent and ready access by the occupants.
Return air registers and supply air grilles should be kept clean and air flow should not be blocked by furniture, carpets, drapes, or other obstructions.
With hot water or steam systems it's important to keep baseboard units and radiators clean and air flow not restricted. Room air needs to circulate freely through the baseboard's fins from underneath and above; and the tops of radiators should not be covered.