MERV Ratings and Efficiency

Minimum efficiency reporting value, commonly known as MERV rating is a measurement scale designed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to rate the effectiveness of air filters.  MERV is the standard used to measure the overall efficiency of a filter, so you commonly see the MERV number on the package when you buy an air filter.  The higher the number, the fewer airborne particles can pass through the filter.  Some of the common particles related to MERV ratings are pet dander, insecticide dust, smog, dust, viruses, wood, tobacco smoke, spores, bacteria and pollen.

MERV ratings are determined in a controlled testing environment.  Particles are placed into an air stream which runs through the test filter.  A laser particle counter samples the air both before and after it is filtered to determine which particles were caught in the filter.  Once the count is completed, a chart is used to set the MERV rating for that type of filter.

MERV ratings range from 1 – 16 and measurements are in microns.

  • Some of the most common filters found in residential use only have a MERV rating of 1-4. These are typically disposable panel type filters and do not do a good job of filtering the air because they will not stop particles smaller than 10 microns.
  • MERV 5-8 rated filters are a better choice and are more commonly found in commercial applications. These filters will collect particles as small as 3 microns and are a good choice for homeowners also.
  • Filters with a MERV rating of 9-12 are used in commercial and industrial applications to stop particles in the 1-3 micron range. These filters are a great choice for homeowners who want the best dust control possible. When using filters with MERV 9 ratings and above it is important to clean or replace them as recommended by the manufacturer because when they clog up they will decrease air flow and operating efficiency.
  • The most efficient filters have MERV ratings of 13-16 and will stop particles as small as .3 microns. These filters are used in hospitals and other super clean environments.
  • Filters with MERV ratings of 17-20 are used in the manufacturing clean rooms for electronics and pharmaceuticals.

If you have any questions about your air filtration system, give us a call at (317) 297-1622, or contact us on-line.   We’ll be glad to give you the benefit of our expertise

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