Cleaning a furnace is not a very difficult job. This is fortunate because it's something you should do at the onset of winter and about once a month thereafter in heavy-use months, generally the coldest ones.
To clean your filter, start by locating your circuit breaker and turning off the power to your furnace [source: Standley]. It's always better to be safe than sorry. Then you must open the panel of your furnace that houses the filter. As noted on the previous page, you might need a screwdriver or some other tool for this part of the job, depending on your model. However, either way it should not be difficult.
Once you find the filter, remove it and examine it. If it's a disposable filter, cleaning is as easy as inserting a new filter and putting the panel back. A disposable filter usually looks like a piece of pleated paper enclosed in a cardboard frame and an open cardboard, metal or wire grid. Some disposable filters are not made of pleated material; these might have a sheet of fiberglass material inside.
If you're running a more environmentally friendly household, however, you'll likely find a permanent, reusable filter. Remove it and examine it. A permanent filter will resemble a disposable filter only slightly, in that it is some type of filtering material enclosed in a frame and grid. Many permanent filters contain several layers of filtration material that surround some sort of anti-microbial core. The frames are made of durable metal, typically aluminum because it will resist corrosion.
To clean a permanent filter, use your vacuum to get the majority of the loose dirt. Then you can use the scrub brush or a damp cloth to remove stubborn particles. If you have access to a shop sink or outdoor hose, go ahead and rinse the entire filter. Make sure you let the filter dry before putting it back in the furnace housing [source: Halas]. Most reusable filters have drain holes to speed up the drying time.
While you're waiting for the filter to dry, use the swabs, toothpicks and toothbrush to clean the area where the filter sits. In addition to replacing or washing the filter, you can also clean the blower assembly and motor housing.
Last but certainly not least, continue reading to become aware of furnace-cleaning safety concerns.