ASHRAE developed the MERV rating system to rate filters on their efficiency. MERV stands for minimum efficiency reporting values. Filters with lower MERV ratings are not as efficient, catching only larger particles. Higher-rated filters can capture smaller particles more efficiently. The current MERV scale ranges from 1-16.
Anything higher than MERV 16 is likely a HEPA filter due to its high performance.
HEPA stands for high-efficiency particulate air and these filters have an equivalent MERV rating of 17 or more. They can capture tiny particles in the 0.3-micron range, including dust, dirt, and pathogens.
They are used to treat critical spaces like protective environments in hospitals.