What is the MERV Rating on Air Filters?

Do you want to know what a MERV rating is? It stands for Minimum Efficiency Report Value and it's an industry standard that measures the overall effectiveness of air filters. A higher rating means that the filter can trap smaller air particles, and with finer filtration, less pollutants in the air are allowed to pass through. The most common air pollutants these filters are tested against usually include pollen, dust mites, mold spores, dust, pet dander, bacteria and tobacco smoke. A MERV 13 filter traps, with its minimum efficiency, less than 75% of air particles that are between 0.3 and 1.0 microns in size.

By increasing the size range of air particles to 3-10 microns, a MERV 13 filter will capture 90% or more of them at their worst. Filters with a MERV rating of 8 to 13 are usually high-end filters for household use or high-quality commercial filters. The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) designed the MERV rating scale to provide a more accurate picture of an air filter's capabilities. The higher MERV rating means that an air filter will capture the most dust, while the lower rating means that a filter will capture the least amount of dust.

A HEPA filter with a MERV 17 rating will trap 99.97% of air particles that are 0.3 microns in size, but will capture an even greater percentage of particles smaller or larger than that size. Efficiency in the standard test method ASW 52.1-92 is a measure of the ability of a filter to remove the stained portion of atmospheric dust from the test air. Detention is a measure of the ability of an air filtration device to remove synthetic dust from the air. The table also uses percentages based on the chances of an air filter capturing dust particles depending on the micron size. Once you understand how the MERV classification chart works, you can choose the air filters with the MERV ratings that are right for you.

These filters will capture a large part of the particles suspended in the air and will improve indoor air quality without significantly increasing energy costs.