Furnace Filter Vs Return Air Filter: Which To Choose?

If you are wondering which to choose between a furnace filter and a return air filter, you’ve come to the right place. We've done the research to bring you the answers you seek.

You do not need to choose between the furnace and the return air filter because your system uses both. They function similarly but are work in different locations. The furnace air filter is in the blower compartment while the return air filter is in the return vents.

In this article, we delve into the similarities and differences between the furnace filter and return air filter to correct the misconception between them. Also, we share some types of filters you may choose for your different air filtration systems. To get started, keep reading!

Technician changing the furnace air filter with a new one, Furnace Filter Vs Return Air Filter: Which To Choose?

How do Furnace and Return Air Filters Works?

Filters for furnaces and return air systems function similarly. Air filters are the hub of a home air filtering system. They are the primary component that ensures the air moving in your house is clean and safe. Here is a step-by-step explanation of how the air filter works or cleans the air in your house.

  1. First, install a clean air filter first in your system. You won't be able to remove the airborne contaminants without a clean air filter. Make sure the air filter you choose fits your AC system properly in terms of size.
  2. Air is pushed through the house as the HVAC system turns on. You can activate your HVAC system in a variety of ways. The air in modern air systems starts to circulate when the ambient temperature settings in your home are changed. 
  3. Air is pushed through the room vents and drawn in through the intake vents. In most situations, the intake is handled by two sizable vents that are placed close to the home's HVAC system.
  4. Air is forced through your air filter as it passes through your intake vents. The air filters will act as a barrier between the circulated air in your home and the filtered air entering your HVAC system.
  5. Small particles are trapped and remain behind as air passes through the filter media. But depends on the filter rating, the higher the filter rating the more particles trap. For some filter types, such as carbon filters, the filter will also sanitize the air and kill undesirable microorganisms.
  6. Clean air keeps flowing to the main AC manifold and is then distributed throughout the house. When the HVAC system is operating, the air filter will constantly capture airborne particles as long as it isn't completely saturated.

Furnace Filter Vs Return Air Filter

Technician removing a furnace filter

A home's central air heating and cooling system are made up of multiple essential parts. Air filters are an essential part of your central air system that allows it to safely cleanse heated or cooled air as it circulates throughout the interior of your home. 

Your central air conditioning system typically employs two different filters to effectively remove undesirable particles, allergens, germs, and other contaminants.

Since "air filters" and other phrases like "ac filters" and "furnace filters" are sometimes used interchangeably, there is a misperception that they are either the same thing or, in certain cases, entirely different things.

Furnace filters and return air filters (AC air filters) are not similar, but they are also not entirely different too. The contrasts between the two are quite distinct. 

Although both filters have the same purpose, which is to clean the air in your home, there are several major distinctions between them. These include the filter's location, lifespan, level of filtration, and price.

To help you choose the best solutions for your house AC, we've outlined the main distinctions between "return air filters" and "furnace filters" in your central air system below.


  • Furnace Filter: Removes a variety of impurities from heated air. Thus, it prevents hazardous airborne contaminants and debris from entering the furnace and heating equipment. Also, it prevents clogs and helps the heating system work cleanly and efficiently.
  • AC Air Filter: Enables the cooled air to be free of pollutants, allergies, bacteria, viruses, dust, mites, and debris. Thus, protects the AC system against hazardous contaminants.  Also, enhances the effectiveness of the AC system. 


  • Furnace Filter: You'll find the furnace filter in your furnace's blower compartment. It is typically in a tray or door on the blower chamber. The air blower is typically in the center of your home, frequently close to your air intake vents

Specialist changing the furnace air filter

  • AC Air Filter: The AC air filter is usually in a slot behind the air return vent. A home may have a vent in more than one location. They are typically on the ceiling of a room in the house, a corridor, or along a staircase.

Technician placing a new furnace filter


  • Furnace Filter: Thickness plays a major role in the lifespan of the furnace filter is significantly. You should change or clean furnace filters that are 1 to 2 inches thick every one to three months. If your filters are 3 to 4 inches, you only need to clean or replace them every 9 months. Additionally, a 6 inches furnace filter has a 12-month lifespan.
  • AC Air Filter: The lifespan of an AC air filter is greatly influenced by the frequency of use, the occupants of the house, and lifestyle. Having said that, under normal conditions you should clean or replace these filters every one to three months.

Filtration Level

  • Furnace Filter: The MERV rating scale indicates the filtration level of furnace filters. Typically, residential furnace filters range from 4 to 12 MERV.
  • AC Air Filter: AC air filters stand out is in the filtration level. From larger waste particles to airborne viruses that are only a few nanometers in size, there is a wide range of filtering. 

The more contaminants the air filter for your AC can remove from the air, the higher the MERV rating. Normal MERV ratings for AC air filters range from 8 to 13.


  • Furnace Filter: Furnace filters typically cost between $15 and $25 for a single filter, although there are many factors to take into account. It will cost more to select a furnace filter with a greater MERV rating or thickness.
  • AC Air Filter: The cost of pleated, fiberglass air filters, which are advised for most household air conditioning systems, varies from less than $5 to $50 per piece. But it is based on the item's size, thickness, and MERV rating.

Different Types Of Filters For Your Air Filtration Systems At Home

Technician changing the furnace filter with a new one

There are various air filters available for various air filtration systems, and each one cleans the air in a somewhat different way. The main categories of whole-house air filters are listed below:

High-Efficiency Particulate Air (HEPA) Filters

They can eliminate dust and mold spores as small as 0.3 microns and at least 99.97% of other airborne contaminants and allergens. It is approved by the Department of Health (DOH).  Any airborne particles, even those as little as microns, including tobacco and pathogens, can be eliminated by them.

Click here to see this True HEPA filter on Amazon.

Ultraviolet (UV) Filters

To eliminate bacteria and viruses, UV filters use short-wave ultraviolet radiation. The UV lamps emit germicidal radiation that cleans the air as it moves through the HVAC system. UV filters can eliminate mold spores and other bacteria that could be harmful to your health.

Click here to see this UV air purifier on Amazon.

Electrostatic Filters

Electrostatic filters generate static using tiny cotton and paper fibers, which attract dust and other airborne particles like a magnet. They are one of the greatest options for people who require a filter that can fight allergens because the magnetism is potent enough to prevent these particles from traveling throughout your house.

Click here to see this electronic air filter on Amazon.

Washable Filters

Washable filters are an affordable way to safeguard the environment, offering both reusable and disposable alternatives. Although this particular type of HVAC air filter has a high initial cost, it is a long-term investment. 

Click here to see these washable and dryer-friendly air filters on Amazon.

Media Filters

Media filters provide additional advantages over regular filters with high MERV ratings when it comes to HVAC system air filters.  These filters offer equivalent filtering efficiency to a high-MERV filter but without the drawbacks of airflow or static pressure. 

Check here to see this media filter on Amazon.

Spun Glass Filters

This kind of filter, one of the most popular kinds of HVAC filters, is made by spinning together strands of fiberglass. Due to its low cost, disposability, and ability to shield furnaces and air conditioners from dirt, it ranks among the finest AC filter kinds. 

Spun glass is one of the most effective AC filters among the various types on the market. However, a more cutting-edge alternative would work better if an air purifier is what you're after.

Click here to see this panel heavy-duty spun glass air filter on Amazon.

Pleated Filters

Materials used in pleated filters for HVAC include polyester textiles and cotton folds. The MERV rating for pleated filters ranges from 5 to 13. They offer less airflow resistive and modest air filtration, but they may filter dust and other contaminants effectively.

Click here to see this MERV 13 pleated air filter on Amazon.

Final Thoughts

Technician changing the furnace air filter with a new one


Furnace and return air filters are different parts located in the blower compartment and return vents respectively. The primary function of the furnace filter is to shield the blower from dirt, grit, pet dander, and other harmful substances.

As for return air filters, not only do they safeguard the HVAC system but they also purify the air you breathe by removing various particles. Just keep in mind to always choose air filters that suit your HVAC system.

Be sure to check out some related posts below!

Can You Clean Home Air Filters Or Should You Replace Them?

How To Change Central Air Conditioner Filter?

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