We all want clean air in our homes. Homeowners invest time comparing furnace filters, air purifiers, and other air filtration devices to improve or maintain indoor air quality. Still, getting everything you need to make an informed decision is hard.

Below, we compare common HVAC air filters with portable air purifiers to help you choose the best mix of options for your home, budget, and health.

Definitions: Furnace Filter vs. Air Filter

One of the biggest hurdles homeowners face is how the industry uses various terms interchangeably.

What Is a Furnace Filter?

Furnace filters are fiberglass sheets inserted into your HVAC stack that remove airborne particles like hair, dust, and allergens from indoor air before it’s distributed throughout your home.

What Is an Air Filter?

Air filters, or air conditioning filters, are fiberglass sheets that trap dust, allergens, and other particulate matter in the air before it is conditioned and blown through the rest of the home. Both air filters and furnace filters are located at the HVAC stack, but air filters do not clean air before it enters the furnace.

So, are furnace filters the same as air filters?

As similar as they sound, furnace filters and air filters aren’t quite the same the same. Both serve the same purpose; they remove potentially harmful (and certainly gross!) particles from your indoor air. The difference between furnace air and air filters comes down to a few key differences.

In some systems, there’s only one filter, but others have separate filters in different locations. If your air filter is located near the return duct of your furnace, you likely only have one filter.

Furnace Filters Air Filters
Function Remove airborne particulates to maintain indoor air quality and prevent damage to the furnace. Filter dust, dander, allergens, and other matter from the air.
Location Usually located near the furnace return duct to treat air before it is heated. Usually located near the return duct of the indoor air conditioning unit, before air is cooled.
Efficiency Often designed to capture smaller particles and measured by “Minimum Efficiency Reporting Value” or MERV. Also measured by MERV ratings, including HEPA-rated filters
Replacement Frequency Replace every 3-6 months Replace every 1-3 months

Why Furnace Air Purification Matters

For homes with central heating equipment, furnace filters are the last line of defense against more than 50 sources of indoor air pollution that can compromise indoor air quality and damage your HVAC equipment, including:

  • Chemicals from cleaning supplies
  • Dust
  • Degrading building materials
  • Mold
  • Pet dander
  • Smoke and particulate matter from cooking
  • Volatile organic compounds (VOCs)

Are Furnace and Air Filters Effective?

Yes. The effectiveness of air and furnace filters depends, however, on how regularly they’re replaced. Along with that, what determines the effectiveness most is the filter’s MERV rating. The MERV of a filter indicates how well it removes debris from the air and what size of particles it’s capable of removing.

Rated on a scale from 1 to 20, air filters with high ratings remove extremely small particles that lower-rated filters can’t. Higher isn’t always better, however: One disadvantage of the highest MERV-rated filters is that they might reduce airflow, forcing your HVAC system to run more frequently and be less energy efficient.

Here’s an example: A filter with a score of 14 removes 90%+ of particles as small as 3 microns and up to 75% of particles 0.3 to 1.0 microns. (A micron is .00003937 inches. Bacteria, for example, are roughly three microns long.)

Air Purifier vs. Air Filter

With furnace and air filters in the mix, having a portable purifier may seem unnecessary. However, the purpose of an air purifier is focused entirely on removing irritants in key areas of the home, often at or near the source. For example, in a bedroom of a child with a dust allergy, or in a kitchen where a gas stove is being used.

How Effective Are Air Purifiers?

While your air filter must clean air from every room in your home from a single, fixed point, portable air purifiers remove irritants from specific rooms at a specific time.

Homeowners put air purifiers at strategic places where there’s an increased likelihood of odors, pet dander, or other sources of contaminants. Some owners sleep with their air purifiers running, leave them on during the day, or keep them primarily in a living space where they spend a lot of time.

However, these devices have their limitations: Air purifiers are only effective at drawing in, purifying, and circulating a limited amount of air at a time. Check the air purifier’s specs to see how many square feet it’s designed to purify – most can handle one or two rooms, at most.

As far as efficiency goes, air purifiers use the same MERV scale as air filters. This means an air filter and an air purifier with a MERV rating of 14 will remove the same kind and amount of air pollutant particles.

Air Purifier vs. Air Filter: What Wins?

This is a case of success by degree. Air purifiers and air filters are both effective in different ways. Air filters treat a higher air volume, while air purifiers provide area-specific filtration.

For serious allergy sufferers or those with underlying respiratory conditions, air purifiers offer additional purification power in rooms where they spend the most time. Since Americans spend roughly 90% of their time inside, air purifiers can be a good idea for anyone looking to breathe better.

Replace Your Filter Regularly (And That Means All Your Filters!)

Whether you use your HVAC system’s air filter alone or a portable air purifier, it’s important to replace filters regularly. Check your owner’s manual to see exactly how often your device needs a new filter – most require replacement every three to six months.

Clear the Air with One Hour Heating & Air Conditioning®

Looking to improve your home’s indoor air quality? Give us a call. The technicians at your local One Hour Heating and Air Conditioning® can help you select the right air filters and explore a range of opportunities to improve your home’s indoor air quality. Want cleaner air? It’s a great day to get started; find a location near you or call (800) 893-3523 today.