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MERV Rating

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Rankin
Rankin Member Posts: 26
in Indoor-Air Quality
I understood that MERV was measured from 1-16. While explaining the filter ratings to a customer, I was interrupted by someone and was told that MERV goes as high as 21.



I've done a little research, and I've found 16 on most websites, but some are showing 20, and one even mentioned it can be infinite.



Can you clear the air for me, Bill?

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  • BillW
    BillW Member Posts: 198
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    MERV numbers

    MERV is the abbreviation for minimum efficiency reporting value of how many particles a particular filter removes. They range from 1 to 16, with the disposable "home center" 1"panels at merv 1-4. Pleated media filters both retail and professional range from 4 to 12, with HEPA (high energy particle arrestance) filters at the top level of 16.  HEPA's are tested using a chemical that produces uniform size particles that are counted both upstream and downstream from the filter.  HEPAS remove about 99% of .3 micron particles.  HEPA-type and HEPA-like are NOT true HEPA filters!  If you are designing a system, remember that the filter will gain resistance as it loads, and especially if you are using HEPAS, size your fans carefully.  Electronic air cleaners don't have a MERV rating. I am not aware of anything higher than MERV16, other than a sheet of 1/2 inch plywood!
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