What Does Mpr Mean On An Air Filter

As much as I've written about filters and filtration in this web log, I have to confess there's i attribute of filter efficiency I've resisted learning about. Every article I've written that mentions filter efficiency talks about only 1 rating scale: Minimum Efficiency Reporting Value (MERV). A couple of other scales are in mutual utilize, likewise, but I just didn't want to know anything almost them because I purchase and recommend MERV rated filters. Only I took the plunge recently, and hither's what you ought to know near the iii main filter rating systems.

Minimum Efficiency Reporting Value – MERV

The standard rating system for filters is called Minimum Efficiency Reporting Value, or MERV. When I say information technology's the "standard" rating arrangement, I hateful it. This rating system is defined in an ASHRAE standard (52.2), which specifies the performance required to meet each MERV level and the testing required. Higher-MERV filters remove more than particles from your air. They also remove smaller particles. A standard fiberglass ane-inch filter is typically a MERV ii. The high end of the scale is MERV-16. (It used to exist twenty, simply ASHRAE dropped information technology to 16 years ago.)

Before we go further, nosotros demand to ascertain the 3 general size ranges of particulate thing (PM).

Range i: 3.0 to x.0 microns (includes PM10)
Range 2: 1.0 to three.0 microns (includes PM2.5)
Range iii: 0.three to 1.0 micron

The words making upwardly the MERV acronym are a bit unwieldy – What did you expect from engineers? – but the "minimum efficiency" part is the near important. For a filter to go the MERV-xiii rating, for example, it must filter out a minimum of 90% of the Range i particles (PM10), a minimum of 85% of the Range 2 particles (PM2.5), and a minimum of 50% of the Range 3 particles. Beneath is a chart from John Semmelhack showing the percentage of particles removed by size range of particle and the MERV rating of the filter.

Equally you can encounter, y'all've got to pace up your filter game to at least MERV-10 to get even half of the PM2.five. But you really should remember of MERV-xiii as the minimum because it removes more than 85% of those particular little bitty invisible pieces of stuff. For the COVID-xix pandemic of 2020, ASHRAE has started recommending at least MERV-xiv.

Filter Performance Rating – FPR

The Dwelling house Depot sells a lot of filters. Rather than employ MERV ratings, though, they decided to create their own rating system. The details of their testing are a scrap murky, every bit their website explains it in broad strokes just. They look at how well a filter catches both large and small particles and rank the filters on a 1 to 10 calibration. From that, they reduce the scale to four numbers (iv, 7, 9, or 10), based on a weighted average calculated according to these percentages:

Sixty percentage of the rating is determined by the filter's ability to capture large particles, thirty percent is determined by its power to capture small particles and weight gain over the filter'south lifetime determines the last ten percent.

Hither are the four FPR ratings you lot'll find on filters at Home Depot:

4 Good
7 Better
9 All-time
x Premium

They must exist using a different definition for the word "best" than the 1 I'm familiar with because their premium is better than best. If you're wondering how FPR compares to MERV, the Home Depot website has a section on that. They start past saying, "FPR 10 is similar in strength to MERV 20, since they are both the highest rating value." They're a scrap out of date, however, because the MERV rating goes up to a maximum of 16 now, not 20. Some filters on their website have both an FPR and a MERV rating, and at least ane with an FPR of 10 is shown as equivalent to either MERV-8 or MERV-13. (Run into screenshot below.) Conspicuously, this isn't clear. Is an FPR-10 the same as MERV-16 or MERV-13 or MERV-8?

They don't provide hands available data on the sizes of what they call large and pocket-size particles, and so information technology's hard to know what you lot're getting with a particular FPR rating. When you combine that with the difficulty of comparing FPR to MERV, it seems the best you can practise with this scale is to use it as a crude guide. And if y'all desire to filter out equally much of the PM2.5 as you lot can, stick with the FPR-10 or find one with that also has a MERV rating and go with MERV-xvi.

Microparticle Performance Rating – MPR

As with Home Depot'southward Filtration Operation Rating, the Microparticle Functioning Rating was adult by a company with a financial involvement in the sale of filters. In this instance, information technology's 3M, the maker of the Filtrete line of filters. Dissimilar the FPR, though, the MPR measures the effectiveness of a filter's capturing only the smallest particles on the MERV scale: 0.iii to one.0 microns. Their website says, "Your filter's MPR (Microparticle Performance Rating) indicates its ability to capture tiny particles between 0.three and one micron in size."

Chances are adept, though, that if a filter captures a lot of the small particles, it volition capture even more than of the larger particles. The scale just won't tell you anything near how well information technology does with particles larger than 1.0 micron. And nosotros should note that 2.5 microns, the upper limit of PM2.5, is in the group of larger particles not covered by MPR. Plainly they do measure the larger particles, however, because they have a folio comparing MPR to MERV, and at that place you can download a table of capture efficiency data showing the 3 ranges of particle sizes used in the MERV calibration.

The MPR organisation, like the other two, uses a numerical calibration on which higher numbers indicate better filtration. The MPR scale, however, uses much larger numbers. Their bones filter is rated at 100 and their most efficient filter is rated at 2800. The MPR-2800 would qualify as a MERV-14, and so even though 3M emphasizes the smallest size range of particles, their best filter doesn't qualify for the highest MERV rating.

My recommendation is to buy filters with a MERV rating whenever possible. All three ratings have their problems but even Home Depot and 3M admit on their websites that MERV is the industry standard for rating filters. Likewise, if yous want the filter to improve your indoor air quality and not just protect the heating and air conditioning system, go with MERV-xiii, FPR-x, MPR-1900, or higher. Just brand certain you lot tin can practise that without reducing air menses and maybe damaging your system.

Allison Bailes of Atlanta, Georgia, is a speaker, writer, edifice science consultant, and founder of Energy Vanguard. He is as well the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.

Related Articles

Tin can Your HVAC System Filter Out Coronavirus?

How Oft Should You Change the HVAC Filter?

seven Reasons Your Filter Isn't Improving Your Indoor Air Quality

Note: Comments are moderated. Your comment will non appear below until approved.