Air Filter vs Furnace Filter

Air Filter VS Furnace Filter: What’s the Difference?

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Do you find that your home has a musty odor that seems to increase the minute you chose to turn on your furnace or cut in your air exchanger system? Perhaps even though you just did your housework, which included dusting, only a day previous; you can visibly see dust and woolies on every surface. Maybe your problems are more on the health side of the spectrum and you find yourself reaching for a nasal spray along with lubricating eye drops the minute your furnace or central air system kicks in. This can be a bother to deal with, irritating and costly if you are purchasing expensive eye drops or duster replacement pads.

A Closer Look

dirty and clean

So, when experiencing any of these issues or all of them at once, it could be because it is time to change the filters of both the central air system and the furnace. These filters have a limited life and should be either cleaned or replaced as per the manufacturer’s instructions. Maybe you are one of those people who didn’t realize your filter would need replacing and it has never been looked at, let alone cleaned.

So what is the difference between your air filter and your furnace filter? Are they the same and serve the same purpose? Is one better than the other? Why do you need a filter? Let’s find out together!

Why Do You Need a Filter? Pros and Cons

Diverse Hands Holding The Word Why?

Depending on the installation set-up of your home, there is a possibility that your air filter and furnace filter will be one in the same. Some homes have a system that will use the same filter and others will have a system that is separately housed but share ductwork and that is it. Some furnace models, especially the older ones, will have a filter directly in the furnace itself, so it is important to ensure that an air filter is present for the central air system.

So why do you need an air filter and/or a furnace filter? There are a few reasons that these are so important and can be seen below.

Image ​Pros ​​Cons
Air filter

Air filter


  • Removes dust mites from the cool air being sent through the duct work of the home
  • Removes allergens and bacteria from the home’s air
  • Enables the central air system to operate at peak performance


  • Can be costly to replace depending on the size of the filter needed for the central air system
  • Depending on the location of the filter, a service technician may be required for changing and maintenance
Furnace filter

Furnace filter


  • Removes dust mites from the warm air that is being sent throughout the home
  • Removes allergens and bacteria from the home’s air
  • Enables the furnace to draw in air to be warmed without any performance issues


  • Can be costly to replace depending on the size of the filter needed for the furnace model
  • Can need frequent replacements depending on the source of heat i.e. a wood furnace needs the filter replacement more frequently than an oil or electric furnace

Air Filter

Senior man opening air conditioning filter in ceiling

The air filter is used primarily when the central air system (the air exchanger and air conditioner) is in use and draws the air from the home into the system to be cleansed by the filter before sending it back out into the atmosphere at a cooler temperature.

This cleansing process involves removing dust mites or other allergens and bacteria that are commonly found in a household before sending it back into the atmosphere. Using a new and proper air filter will allow the occupants of the home to breathe clean air and control the air quality. If during the warmer months you love to open your windows and breathe in the fresh air, an air exchanger is a great way to remove allergens or pollen from your home. People who have existing respiratory issues should notice a reduction in symptoms once the air filter is either cleaned or replaced.

A clogged air filter can also affect the performance of your air exchanger and/or air conditioner. Overheating can become common because the internal components of the system are in overdrive to move the air past the clogged filter causing a failure in the system. Then costly repairs are needed or depending on the level of damage? Complete replacement.

Furnace Filter

Taking Out A Dirty Furnace Filter

The furnace filter serves the same purpose as the air filter as it removes dust, allergens, bacteria and even germs from the air that is drawn into the furnace from the home. This air is what is heated to a desired temperature before it is sent by the use of a blower and fan system into each room via ductwork to ward off the chill of colder months. This air can be heated via propane, electricity, wood or even oil but without a proper filtration system; the air is warm but it isn’t clean.

A clogged or dirty furnace filter can cause issues in the performance of the furnace as the air from the home is unable to make it through the canals to the heating elements. Once it does, the durance needs to work harder to push the heated air back through the canals to be sent throughout the house. This means that you are suddenly burning more oil or wood, using a high level of propane or burning through more electricity and it shows on the monthly bills. Overheating can also happen which can burn through the internal operating system of the furnace and suddenly the motor or blower gives up completely or the sensors that gauge the temperature of the air are kaput and need to be replaced at a significant cost.


Now that we have discovered how both the air filter and furnace filter affects our air quality, it is easy to see the important role that each of them plays in the household. To ensure that the air you and your loved ones are breathing in on a daily basis, regardless of the month or system in use, you need to have some sort of filtration in place. The air filter and the furnace filter will remove any allergens or bacteria from the air you are breathing, allowing for a more restful sleep and an alert morning!

Consult the instruction manual that came with your central air system and the booklet that would have been included with your furnace to schedule out when your filters are going to either cleaned or changed. When filters are clogged with germs and dust, the operating performance of both the central air system and the furnace are affected. Overheating can happen due to the machine working overtime to reach its criteria of clean air and these over-workings can be seen on your monthly utility bill.

There are numerous allergens and germs that exist in the air all around us, from outdoors to work to the grocery store. Shouldn’t we have one place that we can go knowing we are breathing the cleanest air we possibly can?

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