Air filters are provided on all forced air furnaces to remove dirt and lint from heated air. This keeps the fan, heat exchanger and air conditioning coil clean. It also helps clean the air of your home as air circulates through the system. Maintenance is based on the type of filter, how often the unit is running and how you use your home.
The air filter may be mounted vertically or horizontally. Location depends on the manufacturer and type of system, but look for the filter in a slot between the return-air duct and the blower. Slide the filter out and hold it up to a bright light. If the filter is filled with dirt and dust to the point that no light shines through, it should be replaced.
A clogged filter reduces the amount of air that can be blown into the house, making the system run longer than it should to get the house warm. Often times, the air filter needs to be changed every month. Children, pets, plants and activity tend to produce more dirt that finds its way into the heating system, so filters may have to be changed more often.