The Furnace and Air Conditioner Filters We Would Buy - The New York Times

Nordic Pure's MERV 12 filters are not the only products that meet all our criteria, but they are perfectly good examples, and they're usually competitively priced and easy to find online. We like that they're genuinely MERV-certified, because unlike the proprietary ratings used by some bigger-name brands, the MERV criteria are publicly available. Being rated MERV 12, the Nordic Pures will remove at least 35 percent of particles in the 0.3-to-1.0-micron range, which includes bacteria and smoke; at least 80 percent of 1.0-to-3.0-micron particles, which include fine dust and soot; and at least 90 percent of larger pollen, dust, pet hair, and lint particles. Again, MERV stands for Minimum Efficiency Reporting Value, so this is the worst performance measured during third-party testing to the ASHRAE 52.2 standard. And again: the MERV test measures a single pass of polluted air through the filter. In your home, the air will continuously recirculate when your HVAC system is, leading to cumulatively greater filtration with each trip through the return registers.