Has it been more than a month since you ventured into your furnace's filter area? Then it's probably time to clean or replace this dust and dirt catcher to prevent you from sneezing your way into winter mornings. A clean filter maximizes your furnace's efficiency and longevity-- and minimizes your energy bills.
If the floor or area near the furnace is a dust-bunny breeding area, vacuum or sweep prior to replacing the filter.
Locate the service panel, usually on the furnace's lower front or side.
Turn off the furnace, then gently pop open or pull down the panel door with your hands; tools usually aren't needed.
Locate the filter--a framed-mesh rectangular screen inserted either horizontally or vertically near the intake-outtake blower.
Slide the filter screen out (see A).
Check for brown, dusty buildup on the mesh screen (or a screen you're unable to see through).
If you have a reusable plastic-frame or metal-frame filter, use a hose to rinse away the dust particles on the screen in the backyard or driveway (see B). Let it dry, then return it to the furnace.
If you have a disposable cardboard-frame filter, write down the size, then throw it away. Buy a new furnace filter of the same size (available at hardware and home supply stores).