Reading a MERV Rating

MERV summarises how efficiently a filter removes particles across defined size ranges, tested under a standard method. A higher number indicates better capture of smaller particles, but the rating is a summary of several band results rather than a single efficiency figure.

Denser media capture more and resist airflow more. Fitting a higher-rated filter to a system not designed for it can reduce delivered airflow enough that total particulate removal falls, despite each pass being more efficient.