MERV (Minimum Efficiency Reporting Value) serves as a test designed to minimize confusion about the performance of air filtration devices by assessing the minimum or worst-case scenario for a product’s effectiveness.
The test evaluates an air filter’s efficiency across three particle size ranges: large particles (3.0 – 10 microns), medium-size particles (1.0 – 3.0 microns), and small particles (0.30 – 1.0 micron). While two products may share the same MERV rating, variations exist in terms of initial particle size efficiency, initial air resistance, air leakage, bypass air, service life, and tested airflow.
The standard requires the test to be conducted at 1200 CFM (Cubic Feet per Minute). However, not all manufacturers adhere to this condition, and reduced airflow can inflate an air filtration device’s MERV rating. It’s essential to note that MERV solely assesses immediate performance, and a product may exhibit a lower MERV as it begins filtering particulate matter. The MERV test also employs test dust containing carbon.