What Is A Furnace Filter

What is a Furnace Filter and How Does it Work?

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If you’ve ever used a furnace before, you understand how hard the machine can actually work. Even if you aren’t too familiar with a furnace, you should know about the important parts of the machine that makes it work. Just like anything that involves heating or cooling, a furnace uses a filter that enables it to push out hot or cold air with as little dust and other pollutants as possible. A common misconception of a furnace filter is that it purifies the air, but unfortunately, it does not. Instead, its main purpose is to protect the blower fan inside the machine from buildup and gunk.

What Are Air Filters For and What Kind of Air Filter Do I Need?

hand holding furnace filter

To put it simply, it is much like an air conditioning/heating filter that you find in home unit systems. The filtering device is used to make sure the machine stays in top-notch quality. The furnace filter does provide some air cleanliness properties, but its specific function is not to keep the air clean. The function of a furnace filter more so revolves around the overall maintenance of the furnace itself, so that hot air or cold air can be pushed out of the coils by way of the furnace fan.

The filter is a unique barrier between the elements and the fan. Since the fan is one of the most important parts of the machine, it needs protection from elements such as dust, grime, pet hair, human hair and other gunky stuff that gets caught in the air. The filter acts as a catcher of all these things to help prevent the fan from getting too full of gunk and non-operable.

How Does a Furnace Filter Work?

Taking out a dirty furnace

A furnace filter is located right behind the air intake area. The air gets sucked into one end of the furnace, and out of the other end, warming or cooling the area.

The unwanted irritants from the air, such as hair, lint, dust, etc. The air filter will help clean the air, but, again, this is not it’s sole purpose. If you need a stronger machine to help with actual air quality, purchasing an air purifier would be your best bet. A filter for an air unit is important for the whole machine to keep working properly. Without a furnace filter, you’d have all kinds of gross stuff getting stuck to the furnace fan, ultimately breaking it if it wasn’t maintained well enough. Plus, without the furnace filter, you’d have all sorts of extra dust and hair flying around the house – not fun or healthy for anyone.

How to Take Care of a Furnace Filter

Much like an air condition unit, a furnace needs its filtering device changed or swapped out about once a month. If you don’t use the furnace as often, then you can go as long as six months without replacing it, but it’s advisable to change out the filter at least once a month to prevent any long-term damage to the machine. Even if the filter doesn’t appear to be dirty, gunk can form from dust and grime repeatedly being blasted against the fan blades, which weights the fan blades down. In order to make sure all is running smoothly, and your furnace isn’t working harder than necessary, your best bet for maintenance is to make sure that the filter is changed each month.

Close up dirty car air conditioner filter

How much is a furnace filter, you ask? It depends. You can save money by investing in a more expensive, washable kind. Or you can save money short term, and opt for disposable ones. Either way, the cost depends on the size and brand.

Filtering devices are available at any home improvement stores or warehouses. If you don’t have any of these stores available nearby, or you just want to make the process easier, you could always go online to find your appropriate filter. You can find virtually all sizes and shapes of filters, just make sure that you are using the correct size since you won’t be able to get a filter that is either too small or too big to work in your machine. You could essentially be causing more harm than good in this situation.

A too big filter won’t fit and would have to be crammed in, potentially causing damage to the machine and let air escape through holes. A filter that is too small would definitely allow dust and other debris to escape through gaps, so the correct filter size and shape are necessary.

Benefits of a well-maintained filter

Techician looking over a furnace with a flashlight before cleaning it.

Properly taking care of your furnace and actively changing out the filter will not only be beneficial for the actual machine, but it will enable your machine to work to its fullest potential and keep your home as hot or cool as you need it to be. This is also a good way to protect your home from bigger pollutants, like hair or dust, but remember – a furnace is not meant to purify the air. A furnace simply keeps the temperature within a space either warm or cool. This is beneficial for keeping your home cool in the hot summer months and warm and toasty in the winter months. This is a great way to make the home comfortable for everyone and proper maintenance will only extend the life of your machine.


So, as you can see, it is very important to know why your unit requires a filtering device, what it does and how to properly care for your filter and machine. You will notice the benefits of the air filtering device within a heating unit right away, even the first time you switch it out. You will notice all the dust, hair and debris it collects and be grateful that all that gunk isn’t being thrown around your actual house! This provides a slightly better environment for people with allergies, especially, or family members that have respiratory issues such as asthma.

Switching out a dirty filter is super easy and definitely isn’t’ hard to do! It’s just a matter of pushing the old one out and placing the new one in. That simple! A process that takes up to three minutes will provide you a month or more of better breathing, will be most cost-effective and provide better temperatures. It’s a win-win for everyone!

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