What is a MERV, MPR, or FPR Rating for AC and Furnace Filters?

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 50-70 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!

BestFilters.com uses the MERV Rating system. We have all standard sizes of AC & Furnace Air Filters available in MERV 8, 10 and 12 ratings. These pleated, 100% synthetic media filters maintain an electrostatic charge to attract and capture fine particulates. In the average American home, the most common air filter is a MERV 4. These are usually the fiberglass furnace filters that you can see through and do not stop particles smaller than 10 microns. These MERV 4 filters will only protect your equipment and will not help with allergens or even larger particles. We do not recommend MERV 4 filters and do not carry them. We do carry MERV 8, 10 and 12 rated pleated filters. Most residential systems are well able to use replacement filters 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.

Its important to note that the MERV Rating is the MINIMUM initial efficiency rating. Its 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.