The Minimum Efficiency Value (MERV) rating for an air filter is a measure of how effectively the filter prevents dust and other contaminants from passing through and into the air stream. MERV indices range from 1 to 16, with 1 being the lowest efficiency and 16 offering the highest. Most aluminum and mesh filters, as well as cheap air filters, fall within this range. The MERV rating is composed of two components.
The first is the ability to remove large particles suspended in the air, or particles between 1 and 10 microns in size. These “big” particles include pet dander, pollen grains, dust mite debris, etc. The second component evaluates the filter's ability to remove submicron particles, that is, those that are smaller than 1 micron in size; this classification is called the microparticle performance rating (MPR). Filters with a MERV index higher than 13 tend to restrict airflow; the higher the MERV, the greater the airflow restriction.
High-efficiency particulate air (HEPA) filters trap even smaller particles at a speed higher than that of the MERV 16 and are generally used in surgical operating rooms, clean rooms, and other contexts that require absolute cleaning. This guide explains in detail what the MERV is and what the different MERV classifications mean for you and your family. Once you understand how the MERV leaderboard works, you'll be able to choose the air filters with the MERV ratings that are right for you.
