How to Clean a Furnace

Service man kneels beside a furnace in a home attic, to inspect it for before winter usage.
Keeping your furnace and furnace filter clean can cut energy costs and extend the life of the system. It’s also a good idea to have your furnace routinely inspected by a professional.­
iStockphoto/Perry Gerenday

­Lately, it seems that your floors, bookcases, coffee table and most every other surface in your home are covered in dust and dirt faster than you can clean them. No matte­r how frequently you sweep, vacuum and clean, you still seem to have an inordinate amount ­of dust all around. So what's behind the dust-bunny boom? The culprit could be your furnace.

Every furnace could probably use a good wipe-down, but when people refer to cleaning a furnace, they are generally being more specific and talking about cleaning the filter. A dirty filter in a furnace can be responsible for extra dust throughout your house. So by replacing or cleaning your furnace filter, you could be cutting down on your cleaning efforts elsewhere. In addition to keeping the air (and surfaces) in your house clean, routine furnace cleaning can cut your energy costs by 5 to 15 percent [source: Peterson].


­Cleaning­ a furnace filter is pretty simple, especially if you just use disposable filters. It shouldn't require any special tools. The most complex thing you might have to wield is a screwdriver, and, depending on the model, that's probably just to remove the front panel of your furnace to get to your filter. Permanent filters require a little more elbow grease, but many would agree the health of our environment is definitely worth that extra effort.

A regular vacuum or a shop vac and a sink or garden hose are some of the most important tools for cleaning a permanent furnace filter. Beyond that, simple household items like toothbrushes, scrub brushes, toothpicks and cotton swabs are also useful to clean the furnace and its vents.

Continue on to the next page to learn the tools needed to clean your furnace.


Tools Needed to Clean a Furnace

­As with just about any do-it-yourself job, the specific tools needed to complete the work can vary depending on the task. When cleaning a furnace, the actual cleaning process -- and tools needed -- should not really vary too much from the ones listed below. As mentioned earlier, you will likely need a screwdriver to remove the safety panel from the front of your furnace to perform the cleaning.

As you get comfortable with cleaning your furnace, you might find some tools listed below work better than others, depending on your model. The tools listed below are just a starting point on what is needed to clean your furnace. Use what works best for you.


The tools needed to clean most furnaces include:

  • Vacuum
  • Toothbrush
  • Toothpicks
  • Cotton swabs
  • Scrub brushes
  • Replacement filters (if you use disposable filters)
  • Rags [source: Halas]

When using a vacuum for this job, it is best to select one with removable attachments. An upright vacuum without a hose is going to be almost useless here, as you want to vacuum debris in various small nooks and crannies of the furnace, not just the actual filter. Have multiple toothpicks and cotton swabs to get in the smallest of areas, and scrub brushes of various sizes will be best to get all of the vents.

Now to the important stuff -- how to clean your furnace. Read on.


Steps for Cleaning a Furnace

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.


Safety Concerns When Cleaning a Furnace

As with any home maintenance work, especially when dealing with appliances, there are safety concerns to consider. When cleaning a furnace, there are a few things you should pay particular attention to.

First, you should always turn the power off before you begin cleaning the furnace -- before you even touch the furnace to open the front panel. Though you won't actually be altering any of the electrical wiring, you are still dealing with the internal workings of your furnace, which may entail having to move some of the wiring to get to your filter [source: Standley].


When you are cleaning the filter (or wiping down any other part of the furnace), be sure not to drip water everywhere. Furthermore, if you choose to rinse down your filter, make certain it is completely dry before reinstalling -- water and electricity don't mix.

When vacuuming or washing the filter, you will most likely encounter a lot of dirt, dust and grime. So, you might want to consider wearing a dust mask.

Lastly, always take care to return everything to its proper place. Make sure you reinstall everything properly, leaving the correct amount of space between the filter, vents or any other equipment within the furnace [source: Hayner]. An improperly configured furnace won't work right, and the consequences can be bad.

To learn more, visit the links on the next page.


Lots More Information

Related HowStuffWorks Articles

  • Dickinson, Marc. "How to Clean Furnace Filter." Service Magic. (Accessed 3/3/09)
  • Halas, Rose. "How to Clean Your Furnace." Essortment. 2002. (Accessed 3/3/09)
  • Hayner, Jan. "Take the Stress Out of Housecleaning." Online Organizing. Nov. 21, 2008. (Accessed 3/3/09)
  • Heloise. "Tidy Up Air Ducts." Good Housekeeping. (Accessed 3/3/09)
  • Lucky Duct. "Furnace Cleaning." (Accessed 3/3/309)
  • National Furnace Heating and Air Conditioning. "Safety and Maintenance." (Accessed 3/3/09)
  • Peterson, Josh. "How to Clean a Furnace Filter." Planet Green. Feb. 6, 2009. (Accessed 3/3/09)
  • Standley, Vincent. "Clean Your Furnace Filter." Green Guide. Jan. 31, 2009. (Accessed 3/3/09)
  • Start Remodeling. "Fall Furnace Cleaning - Maintenance." (Accessed 3/3/09)
  • Taylor, Glenn. "A Furnace Clean-and-Check Primer." Contracting Business. Nov. 1, 2004. (Accessed 3/3/09)