The fact is not all air filters are created equal. The cheapest filters might be fine for filtering out large sized household dust and lint, but the typical home's interior air is polluted with a lot more unwanted elements composed of much very fine size. The EPA provides an informative breakdown of particulate matter and gaseous pollutants often found indoors, listing the "two categories of indoor air pollutants that can affect the quality of air in a home." Viruses, bacteria, pollen, mold, dust mite, animal dander, smoke...nobody wants to breathe these inside their own home and the cheapest of HVAC filters do a poor job of removing these elements from interior air.
So what should a buyer look for when shopping for an air filter effective against a wide variety of particulates and pollutants? Fortunately, there are ratings systems to help compare the level of protection air filters provide. Unfortunately, many groups, stores, and manufactures tout their own rating systems, which means choosing the right HVAC air filter takes a little cross-referencing and research.
The American Society of Heating, Refigeration and Air-Conditioning Engineers (ASHRAE) designed a rating system known as Minimum Efficiency Reporting Value (MERV). MERV ratings run from 1-20, designating the effectiveness of filers to capture smaller and smaller minimum particle sizes. The higher the MERV rating, the better, and we recommend this rating system the best for determining filter efficiency.
Big brand, Filtrete, uses their own Microparticle Performance Rating (MPR), rating their filters based upon air filtration efficacy. Their basic system simply groups filters into "good (300 MPR)", "better (600 MPR)", and "best (1,000 MPR)" - with "best" capturing "at least 90% of large particles from the air passing through the filter." Their MPR rating is unfortunately only useful if purchasing their brand of air filters.
The Home Depot's Air Filter Performance Rating (FPR) System below aims to make it even easier to compare brands by presenting a unified ranking system in an easy-to-read chart/rating based upon the filters' 1) ability to capture large particles, 2) ability to capture small particles, 3) and weight gain (filter lifetime). But the FPR rating system lacks specific figures for the sake of simplicity.
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