MERV Ratings

MERV rating chart with contaminant capture coverage

We often get asked, "What is MERV?"


MERV is an acronym for "Minimum Efficiency Reporting Value". The MERV filter rating system was devised by the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) to standardize and simplify air filter efficiency ratings for the public.

MERV ratings are determined in a standard laboratory test measuring how well air filters capture and hold airborne particles of a wide range of sizes. Dust, soot, pollen, smoke, and pet and human dander are a few of the types of particulate pollutants that may be found in indoor air. These particles can range in size from less than 1 micron (or millionth of a meter) to more than 10 microns. Simply put, MERV ratings are determined by what comes out compares to what went into the filter during standardized testing.

MERV ratings are useful in comparing different mechanical filter products. In general, the higher the MERV rating, the more efficiently the filter initially performs in removing smaller particles. 


However, because of the smaller pore sizes needed to capture smaller particles, air does not flow as easily through a higher MERV filter. We recommend you take the performance of your HVAC unit into account when choosing which MERV rating is right for you. 

ASHRAE Standard 52.5 minimum efficiency reporting value MERV rating chart with particle size in micrometers