What Is the MERV Rating System for Air Filters?

The MERV rating, which stands for Minimum Efficiency Reporting Value, is a standardized scale used to measure the effectiveness of air filters in capturing particles of specific sizes. The MERV rating system was developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). ASHRAE has developed filter efficiency and testing standards that are used for all types of air filters, including HVAC filters and filters used in industrial air filtration and ventilation. For cartridge filters in dust collectors, the MERV rating indicates how efficiently the filter captures airborne particles. MERV ratings range from 1 (least efficient) to 20 (most efficient). (Note: MERV ratings above 16 are equivalent to HEPA filtration; the highest rating typically used for industrial air filtration is MERV 16.) The higher the MERV rating, the finer the particles the filter can capture. Manufacturers must have their cartridge filters tested by a third-party laboratory using ASHRAE-approved testing methods to use the MERV rating system.