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MERV, MPR, FPR: the ABCs of air filter rating systems

Understanding the different air filter rating systems and how they compare

Have you wondered why there are three different rating systems? Certain brands have created their own rating system but, at the end of the day, they are rating the same filter. Unaware consumers often find themselves paying premium prices at grocery stores or big box retailers. Learn the facts and your next purchase will be much easier on your wallet.

FPR

Filter Performance Rating is a rating system developed by The Home Depot for brands sold through their stores to indicate whether a filter’s performance is considered good, better, best or premium.

    Good: FPR 4–5
  • Traps household dust and lint, dust mites, pollen, pet dander
    Better: FPR 6–7
  • Traps household dust and lint, dust mites, pollen, pet dander, bacteria, mold spores
    Best: FPR 8–9
  • Traps household dust and lint, dust mites, pollen, pet dander, bacteria, mold spores, smoke, smog, microscopic allergens, plus particles that can carry viruses
    Premium: FPR 10
  • Traps household dust and lint, dust mites, pollen, pet dander, bacteria, mold spores, smoke, smog, microscopic allergens, plus particles that can carry viruses, particles that can carry odors

HEPA

High Efficiency Particulate Air filters must remove 99.97% of particles as small as 0.3 microns to meet filter guidelines set by the US Department of Energy. The HEPA rating only applies to air purifiers; it’s not used for furnace or air conditioner filters.

MERV

The minimum efficiency reporting value — or MERV — is a rating system developed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers out of a need to evaluate the effectiveness of air filters. Using a scale of one to 20, MERV measures a filter’s ability to capture unwanted airborne particles, as well as the size of the particles. The greater the percent of unwanted particles captured, and the smaller their size, the higher the rating. For example, a MERV 3-rated filter can remove only a small percent of the largest airborne particles, while a MERV 15 filter can trap some of the tiniest airborne particles.

    Basic: MERV 6
  • Traps household dust and lint, pet dander and mold spores
    Advanced: MERV 8
  • Traps household dust and lint, pet dander, mold spores, pollen, dust mites, fine dust
    Premium: MERV 11
  • Traps house dust and lint, pet dander, mold spores, pollen, dust mites, fine dust, auto emissions
    Ultimate: MERV 13
  • Traps house dust and lint, pet dander, mold spores, pollen, dust mites, fine dust, auto emissions, smoke, tobacco smoke, bacteria, very fine dust, odor

MPR

Micro-Particle Performance Rating is a metric developed by 3M Filtrete indicating how effectively a filter can capture particles between 0.3 and 1 micron in size. MPR is a metric indicating good, better and best, with filters containing the highest MPR (1900 or greater) being the most effective at filtering airborne particles.

    Basic: MPR 300
  • Traps lint, household dust, pollen
    Good: MPR 600
  • Traps lint, household dust, pollen, dust mite debris
    Better: MPR 1000
  • Traps lint, household dust, pollen, dust mite debris, mold spores, pet dander, smog, smoke
    Best: MPR 1500
  • Traps lint, household dust, pollen, dust mite debris, mold spores, pet dander, smog, smoke, bacteria, viruses
    Maximum: MPR 1900
  • Traps lint, household dust, pollen, dust mite debris, mold spores, pet dander, smog, smoke, bacteria, viruses, odors

This grid illustrates how the ratings compare to one other:

MERV MPR FPR
6 300 N/A
8 600 4–5
11 1,000 6-7
12-13 1,500+ 8-10

AIR FILTER FAQ

What size filter do I need?

The model number and size of your air filter will likely be printed on the filter itself. If not, some quick measurements will tell you what size replacement to buy (common sizes include 20x25x5, 20x25x1, 24x24x1 and 16x20x1.) In addition to length and width, filters come with different thicknesses, typically ranging from one to four inches. A thicker air filter will help to trap more particles, but it may not fit your furnace or air conditioner. And in some cases, a thicker air filter may also impede airflow. Check the thickness of your current filter or look at the user manual to find out what the system can support. If your furnace or AC will only accommodate a one-inch sized filter, you can maximize its effectiveness by checking it at least every 30 days and replacing it when it’s getting dirty.

What’s the difference between air filter brands?

Determining what brand to use in your heating and cooling system is ultimately about function and performance — not brand name. The difference between air filter brands is skin deep. Frequently made from the same types of raw material and designed to perform the same task, look beyond the brand. Choose the air filter that’s best for your needs by considering the filter’s rating, reading the product specs and knowing the particles you want removed from your air.

How often should I change my air filter?

The standard response to this question is: it depends. The lifespan of a filter depends on the type of media its made of, your air quality and the contaminants within your home, and where you live. While the general rule of thumb is every 3 months, the best thing to do is check your air filter at least once per month. If it’s getting dirty and clogged, replace it with a new one. Pro tip: Whenever you buy a replacement filter, get at least two. That way you’ll always have a clean filter on hand.

Why should I change the filter on time?

As the filter reaches the end of its life, the clogging makes the fan work harder and harder to push the air through the filter. This restriction can reduce the airflow through the house, and may affect the performance of the heating and cooling system.

Can I wash or vacuum the air filter?

No, cleaning your air filter is not a safe or effective alternative to filter replacement. The unique filter fibers are not meant to get wet, and can be damaged or destroyed when washed. Additionally, exposure to water can significantly increase the presence of mold and bacteria in the filter, which would then be released into the air. Vacuuming isn’t recommended because the delicate filter fibers can be easily torn or ripped. Because a vacuum isn’t powerful enough to remove all the impurities trapped in a filter, it won’t truly be clean and may release the unwanted particles into the heating or cooling system.

What is a pleated filter?

The most common distinction of a pleated air filter is also the most obvious. A pleated air filter, unlike its flat fiberglass style, doubles the amount of fabric to provide more surface area to capture airborne pollutants. As a result, it will have a naturally higher MERV rating, helping to reduce more pollutants from making it into your air.