What is an efficiency or MERV rating?
Most filters are labeled with a MERV (Minimum Efficiency Reporting Value) rating number, which measures a filter's ability to trap particles ranging in size from 3.0 microns to 10.0 microns.

Residential filters commonly have MERV ratings of 1-11. The higher the MERV rating, the more efficient the filter is, and the more particles it can filter.
• A MERV rating of 6 means the filter is 35% to 50% minimum efficient at capturing particles, sized 3.0-10.0 microns.
• A MERV rating of 7 means the filter is 50% to 70% minimum efficient at capturing particles, sized 3.0-10.0 microns.
• A MERV rating of 8 means the filter is 70% minimum efficient at capturing particles, sized 3.0-10.0 microns.
• A MERV rating of 11 means the filter is 85% minimum efficient at capturing particles, sized 3.0-10.0 microns.

MERV is an industry standard rating, so it can be used to compare filters made by different companies.

АкщьЖ http://www.aafilters.com/customerservice.htm

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Note added at 14 mins (2007-06-01 22:06:07 GMT)
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При переводе на русский так и используется: Высокоэффективные фильтры - 90-95 % (MERV 14), 95 % (MERV 15), 95 % DOP (MERV 16) (cм. "Защита приточного воздуха от заражения химическими и биологическими агентами" @ http://www.abok.ru/for_spec/articles.php?nid=2029