THE DEFINITIVE GUIDE TO AIR FILTER RATINGS: MERV vs. MPR vs. FPR
If you’re looking for MERV, MPR, and FPR explanations for air filters, look no further. This is the most comprehensive explanation on the web, including what the acronyms stand for, what they actually mean, how they compare to each other, and much more. So let’s get to it.
What do MERV, MPR, and FPR stand for and where do they come from?
MERV = Minimum Efficiency Reporting Value. Regulated by standards set by ASHRAE (the American Society of Heating, Refrigerating, and Air conditioning Engineers), every single furnace filter for sale in the US contains a MERV rating. This is the only nationally regulated, independent rating system for air filters.
MPR = Microparticle Performance Rating. The MPR system of ratings was created by and is only used by 3M. Only filters under the 3M / Filtrete brand contain an MPR rating.
FPR = Filter Performance Rating. FPR is a proprietary system developed and used only by filters sold at The Home Depot. They made the switch from MERV several years ago.
So what exactly does each rating system mean? How do they differ?
Excellent questions, and there really is no simple answer, so I’m going to break it down by talking about each rating system individually.
MERV Rating: MERV ratings range from 1-16, and the rating is designed to measure the worst-case performance of a rated air filter on particles in the size range of .3 to 10 microns. (Note: As a point of reference, an average human hair has a diameter of 40-50 microns.) The rating works on three tiers, and the rating depicts what percentage of particles are removed in the 3.0-10.0 micron range (known as E3), 1.0-3.0 micron range (known as E2), and .3-1.0 micron range (known as E1). Take a look at the chart below and then let’s walk through a couple of examples:
Example #1: In order to achieve a MERV 8 rating, a filter must remove greater than 70% of all particles in the 3.0-10.0 micron size range (E3), which includes mold spores, hair spray, pet dander, etc. A MERV 8 filter must also remove greater than 20% of particles in the 1.0-3.0 micron size range (E2), which includes insecticide dust, asbestos, bacteria, house dust, skin flakes, etc. For a MERV 8 filter, there is no minimum removal efficiency for particles in the .3-1.0 micron size range (E1).
Example #2: In order to achieve a MERV 13 rating, a filter must remove over 90% of particles in the 3.0-10.0 micron range (E3), over 85% of particles between the size of 1.0-3.0 microns (E2), and over 50% of all particles in the .30-1.0 micron range (E1), which includes lead dust, auto emissions, smog, oil smoke, tobacco smoke, and cooking and grease smoke, to name a few contaminants.
A few takeaways here. First, your filter will not be able to remove 100% of any one particle in the air. That said, a higher MERV rating does tell you that a filter removes a higher percentage of a specific particle as well as removing a larger variety of particles from the air. Second, if you’re using a cheapo blue fiberglass filter that cost $1-ish, you’re removing – at most – 35% of all particles measured in the 3.0-10.0 size range (E3), and far less than that (it’s unmeasured) for E2 and E1. Why even have a filter? You might think you’re saving money, but this is going to cost you in the long haul when your furnace breaks down.
MPR Rating: MPR is the rating system created by 3M, and only 3M filters possess an MPR rating. Convenient, isn’t it? We have a $30 billion company with an unlimited marketing budget that is trying to monopolize the residential air filter market by pimping their own rating system. I don’t blame them for the effort – I would do the same thing if I were in their position. But the fact of the matter is it’s purely marketing. After all, when it comes to their commercial air filtration products, they stick to MERV ratings and drop these MPR shenanigans. Don’t believe me? Click here to check out some of their commercial offerings.
Straight from 3M’s website, here’s all they have to say about MPR:
“3M developed the Microparticle Performance Rating (MPR) system to demonstrate a filter’s ability to capture the smallest airborne particles—from 0.3 to 1 micron in size from the air passing through the filter. The MPR system helps you compare Filtrete filters based on the level of air filtration you want. The higher the MPR, the better the filter’s ability to capture particles from the air as it passes through the filter.
MPR is different from MERV, the Minimum Efficiency Reporting Value. The MERV system measures a filter’s ability to capture large particles. The MPR only takes into account the tiny microscopic particles between 0.3 and 1 microns.”
If you’ve forgotten, go back and read the MERV section above. MERV, the only universal standard regulated by an independent third party, takes into account tiny microscopic particles in addition to the larger particles. Here’s the kicker, too. 3M wants to convince you that those larger particles don’t matter, but they do, because they affect airflow in your system. If a filter is designed only to filter out tiny microscopic particles, it will likely restrict airflow to your system, straining your unit and increasing the chances of a breakdown.
Furthermore, when you hear or read someone say the MPR 600 is the “equivalent” of a MERV 8 filter, nobody can be sure about that unless he or she has seen the “third party test reports” that 3M talks about. You see, 3M says their ratings depend on filter efficiency at the microscopic levels of .3-1.0 microns (E1, not incidentally), but MERV 8 filters do not have a minimum efficiency requirement at the E1 size level, so there’s no comparison possible – it’s pure marketing propaganda. In order to be equivalent to a MERV 8 filter, one would need to know what the E3 and E2 efficiency numbers are, but that’s impossible. Filtrete’s enemy in the market is the educated air filter consumer.
Lastly, let’s touch on those “third party” test reports 3M talks about. Until they want to publish their “third-party” tests, nobody can verify the legitimacy of the claims they make. Full, independent test reports (ASHRAE 52.2 testing) cost about $2,500+ per filter. 3M, a $30 billion company, isn’t willing to publish those test reports. Why not? They could test 40 filters for $100,000, which is about .000333% of their total revenue. What are they afraid of? Maybe nothing, but simply publishing the test reports would add some credibility to their rating system. Instead, though, 3M chose to create their own system so that you cannot compare their filters to the universal standard of MERV.
FPR Rating: Developed by The Home Depot for brands sold in their stores, the FPR rating is just slightly better than MPR, and it’s a noble effort by The Home Depot to confuse the customer and lock them into their filters. The fact that they used to use MERV until about 2013 should say enough, but let’s discuss FPR at greater length – it’s actually not the worst thing I’ve seen.
One major blow to the FPR system is that nobody has seen the information “tested by an independent third-party lab.” Sounds familiar, right? No third party verification and a rating system completely made up by a large company…got it.
That said, The Home Depot’s FPR does at least account for larger particles, unlike 3M’s MPR, which measures .30-1.0 micron particles and nothing more. So how does the FPR stratify it? Straight from The Home Depot’s website, they measure:
- ability to capture large particles
- ability to capture small particles
- and weight gain (filter lifetime)
The results of this testing were weighted in a scale as follows:
- Large Particle Capture: 60%
- Small Particle Capture: 30%
- Weight Gain/Lifetime: 10%
On the surface, this looks legit. Dig a little deeper, however, and it’s only slightly better than 3M’s MPR system. First, what defines a large particle and what defines a small particle? No sizes or size ranges are given, so comparing this to MERV is again impossible – we are left to trust The Home Depot’s own cross-referencing. Second, the weight-gain/lifetime is an interesting angle to play, but ASHRAE’s full performance test (52.2) also measures “dust holding capacity” (DHC), which is the same thing that Home Depot is promoting here. That said, this “weight gain/lifetime” has no effect on the effectiveness of the filter to do its job – filter particulate – in any way. That said, I have no problem with them including it in their arbitrary equation.
Regardless, The Home Depot publishes this nice little graphic to help you pick out your filter in the store:
As you can see, they try very hard to correlate their rating system to the particulate that MERV 8, 11, and 13 filters remove from the air. Does that mean that these filters are MERV 8, 11, and 13? Absolutely not, because nobody has seen the requirements they use for “large” and “small” particles, and we don’t know what the E3, E2, and E1 efficiencies are or how they are measured by the FPR.
And let me say something about the “Premium” filter here: don’t fall for the odor-removing pleated filters. Having worked in commercial air filtration, the effect a carbon pleat has on odor removal is minimal. The activated carbon will be fully “used up” within hours, not months, effectively rendering that benefit useless. Now you know.
That was interesting…can you just tell me why are there three different rating systems?
I’m trying to be as objective as possible here, but as an air filtration professional who spent 3 years in the commercial and residential manufacturing side of the industry, I can think of only two reasons to deviate from the universal industry standard (MERV). The first reason (in my opinion) is that FPR and MPR are purely marketing gimmicks intended to complicate the purchasing and comparison process. 3M and The Home Depot are looking to capitalize on the trust and brand equity they have built and are hoping to hook you in to buying their ratings and monopolize people’s business that way. The second reason, and far more nefarious (again, this is just my opinion), is that they very well might be selling you a drastically inferior filter without giving you the means to compare it to others (in this case, those “means” would be a MERV rating).
Who are two of the largest brands in all of residential air filters: The Home Depot and Filtrete. When you hold a big chunk of the market and are a very trusted brand (like HD and 3M), you have an opportunity to create your own standards. The only thing I’m surprised by is that they didn’t collude to use one system – after all, Filtrete owns serious shelf space in The Home Depot.
So I ask you: is this simply a marketing gimmick, or are they selling us drastically inferior filters? In my own educated opinion – without being able to see the test results – I would probably say a little bit of both. Why else won’t they publish the test results?
So…can’t you just give me a comparison chart for MERV, MPR, and FPR?
I can, and I will. I just wanted to go through that so you understand the comparison chart below, which is based on subjective ratings and cross-references made by the companies that subjectively rated the filters. So without further ado…here’s a MERV, FPR, and MPR cross-reference chart:
Do I believe the FPR and MPR MERV 8 “equivalents” are just that? No, I do not, and I don’t really have much to gain by convincing you of that. Sure, we would love to have your business at FilterSnap, but at the end of the day we don’t really compete with The Home Depot and Filtrete; we sell air filter subscriptions, delivering air filters to your home when it’s time to change them. Convenient isn’t it?
If you’re looking for which filter you should buy, I would recommend any MERV-rated filter – there’s nothing to hide behind. Check out our helpful selection chart below to see what level might be best for you:
Got questions? Ask below in the comments.