MERV
Minimum Efficiency Reporting Value · MERV 13
MERV (Minimum Efficiency Reporting Value) rates an air filter's ability to capture particles between 0.3 and 10 microns; a MERV 13 filter captures at least 50% of particles from 0.3 to 1.0 µm.
MERV comes from a test method developed by ASHRAE. The higher the number, the higher the filter’s capture efficiency for most particle sizes. EPA’s figures for a MERV 13 filter: at least 50% of particles from 0.3 to 1.0 µm, at least 85% from 1.0 to 3.0 µm, and at least 90% from 3.0 to 10.0 µm.
EPA recommends a filter of at least MERV 13, or as high a rating as the system fan and filter slot can accommodate, including during wildfire smoke. Denser filters restrict airflow, so EPA suggests asking an HVAC technician which is the highest-efficiency filter that works for a given system.
MERV applies to filters in a central system. Portable air cleaners are compared by their clean air delivery rate instead.
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