It's that time - time to replace the air filter on your furnace. For the average home, this should be done now as fall begins, and again in three months. The reason is that a dirty filter restricts airflow through your heating system. Reduced airflow can mean uneven heating or cooling, increased fuel bills, and added stress on your furnace.
To replace the filter:
Locate the filter. It's usually where the cold air enters the furnace, near the fan section. At this location, the air is flowing into the furnace. The airflow arrow on the filter should point toward the furnace. Slide the filter out and note its size. It's written on it somewhere. Buy a half-dozen filters from the hardware store.
Replace the filter now and check it monthly. Replace it as needed, but at least every three months - more often if you have fur-kids! The rate at which they get dirty depends on the number of people, pets and amount of dust in your home. You might want to consider an electronic air filter if you have a family member who suffers from allergies or one who smokes. Electronic air filters do a great job of taking very small particles out of the air, but because they do a better job of cleaning, they get dirty faster. They should be cleaned once a month.
-Sourced from Sears Manage My Home