Understanding Filter Ratings: MERV, FPR, and MPR

Most discussions about filter efficiency refer to only one rating scale:  Minimum Efficiency Reporting Value (MERV). But as Allison Bailes points out in this recent Energy Vanguard blog post, there are a couple of other scales - FPR and MPR - that you probably need to know about. FPR (for Filter Performance Rating) is the rating system used by Home Depot, while MPR (for MIcroparticle Performance Rating) is the rating system developed by 3M, the makers of Filtrete filters.

Basically, says Bailes, each rating system attempts to compare not only the size of the particulate matter that the filter can block, but also the percentage of particles within each of three distinct size ranges: Large ( 3.0 to 10.0 microns); Medium (1.0 to 3.0 microns); and Small (0.3 to 1.0 microns). Bailes notes that all three ratings have their problems, but because MERV is the industry standard for rating filters, he recommends buying filters with a MERV rating whenever possible. Writes Bailes: "Think of MERV-13 as the minimum because it removes more than 85% of the smallest particulate matter. For the COVID-19 pandemic of 2020, ASHRAE has started recommending at least MERV-14."