ASHRAE Terminology

A Comprehensive Glossary of Terms for the Built Environment
ashrae.org/ashraeterms

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minimum efficiency reporting values (MERV)

scaled rating of the effectiveness of air filters. The scale is designed to represent the worst-case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometers. The MERV rating is from 1 to 16. Higher MERV ratings correspond to a greater percentage of particles captured on each pass, with a MERV rating of 16 filter capturing more than 95% of particles over the full range.