What does a MERV Filter rating mean to me?

One Day, some years ago, I fell asleep and the world changed on me…well, this happens often to me as I’m getting up there in age and the HVAC world evolves. This happened to me on the filter efficiency ratings as one of our younger engineers corrected me on filter efficiency to MERV ratings and handed me the MERV Rating chart (below)…

For an old dog engineer it was time for me to learn the meaning of MERV Ratings as it is the standard of the HVAC Filter industry (ASHRAE Standard 52.2 Filter Testing) …

The acronym MERV stands for “Minimum Efficiency Reporting Values”. MERV ratings are now used to rate the ability of an HVAC air filter to remove certain sized dust particles as the particles pass through the filter. This has always been the case even with the old scale filter efficiency ratings. However, now the filter industry has a well-defined MERV efficiency scale from 1 to 20 and every filter manufacturer must comply with the dust spot efficiency and particle size of the controlled contaminants through testing in order to classify their filters to a MERV rating.

MERV-20 has the greatest rating 99.999% efficiency on .10-.20 pm and is commonly seen in Class-10K to 100 clean rooms.  Whereas MERV-1 is less than 20% efficiency and is often found on window A/C units.

Below is the MERV Rating Chart that can be useful to determine the right filter needs for your HVAC application.

MERV filter rating

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