The Minimum Efficiency Report Values (MERV) indicate the ability of a filter to capture particles between 0.3 and 10 microns (µm). The MERV 1 rating is the lowest efficiency with minimal filtration, while rating 16 offers the highest efficiency and filtration. A high MERV rating means more particulate matter will be removed from the air, so you might think that air filters with the highest MERV rating are the best. MERV 5 to 8 filters provide good filtration and remove most pollen, mold spores and dust mites.
MERV 10 to 12 air filters are capable of trapping particles down to 1 micron, such as car exhaust, pollen and mold spores. Although ASHRAE recommends MERV models 13 and 14, it's best to select a filter with the highest possible MERV rating for your specific air conditioning system. The optimal MERV rating for capturing particles smaller than 1 and no larger than 3 microns is 9 to 12. This range of MERV ratings is sufficient to capture particles such as pollen, mold spores, legionella and humidifier dust.
