Posted by Richard Farkas on 2/20/2014 to Air Quality and Air Purification
At Bestfilters.com we often get calls from people looking to replace the filters on their air conditioners and furnaces and who wonder about the ratings they see on them. These ratings are especially important as they help determine the air quality in your home, when it’s sealed up either during the winter or the hot days of summer.
A dirty filter can affect the quality of the air in your home and your air conditioner and furnace to operate inefficiently. You should buy replacement filters on a regular basis. How often to replace often depends on the quality of the filter you buy. Cheaper filters must be replaced more often.
The MERV Rating is the accepted Minimum Efficiency Reporting Value for air conditioner furnace filter media as determined by the American Society of Heating, Refrigerating, and Air Conditioning Engineers, (ASHRAE). MERV is the primary international air conditioner furnace filter industry standard and is used for rating the ability of a furnace filter to capture and hold particles and pollutants. The measurement used in these ratings is a Micrometer, or micron.
• A micron is one millionth of a meter (0.000001m) and is not visible to the human eye.
• A piece of copy paper is about 100 microns thick.
• A human hair averages 80 microns in diameter.
• Pet dander is 2-4 microns in size and can linger in the air for hours before it settles on a surface!
A filter can have a MERV rating as low as 4 or as high as 13. Most homes filters have a MERV rating of 4. The problem with these is that they are designed more to protect the unit, then to clean the air. They do not help with allergens or larger particles.
At Bestilters.com don’t even carry filters with this low of a rating. We recommend MERV 8, 10 and 12 rated pleated filters. Most residential systems are well able to use up to MERV 12.
• MERV Rating is the established air filter industry rating system, but, some companies have developed their own rating systems, based on the ASHRAE MERV Rating.
• MPR Rating, or Microparticle Performance Rating, was developed by a large manufacturer (3M) to grade their air filters based on the ability to filter air particles smaller than 1 micron. The microparticle performance rating is not considered to be the industry standard by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE). The published MPR Rating numbering system is a scale of 0 2700, with their highest published furnace filter equaling a MERV 13. • FPR Rating, or air Filter Performance Rating, is a grading system that uses a color/number system on a scale of 4 (green circle) to 10 (blue circle). Some of their air conditioner filter descriptions refer to the MERV Rating and the MPR Rating, but don't always agree. It’s important to note that the MERV Rating is the MINIMUM initial efficiency rating. It’s the efficiency rating given to an air conditioner furnace filter when it is brand new, as the new air conditioner furnace filter traps more debris, it actually and somewhat surprisingly, becomes more efficient at trapping particles as time goes by. Eventually, though, every air filter will trap the very tiny particles until it becomes so dirty that air cannot get through and if the filter is not replaced prior to this point, significant damage may occur to your HVAC or furnace .