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MERV Ratings Explained

Recently the American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) and the air filter industry have come up with a standardized rating system, based on the European concept, of a MERV rating for each type of air filter. This numbering system makes it easier to evaluate and compare mechanical air filters and will hopefully eliminate some of the confusion regarding the overall effectiveness of any type of a mechanical air filter on removing airborne particulates, especially those that are less than 2 microns in size.
Minimum Efficiency Reporting Values (MERV)
  

Group
Number
MERV
Rating		 E1
Average Particle
Size Efficiency (PSE)
0.3-1.0 Microns		 E2
Average particle
Size Efficiency (PSE)
1.0-3.0 Microns		 E3
Average Particle
Size Efficiency (PSE)
3.0-10.0 Microns
Average Arrestance
(ASHRAE 52.1)
Minimum Final
Resistance
(in. W.G.)		  
1 MERV 1
MERV 2
MERV 3
MERV 4		 -
-
-
-		 -
-
-
-		 Less than 20%
Less than 20%
Less than 20%
Less than 20%		 Less than 65%
65-36.9%
70-74.9%
75% or greater		 0.3m
0.3m
0.3m
0.3m		  
2 MERV 5
MERV 6
MERV 7
MERV 8		 -
-
-
-		 -
-
-
-		 20%-34.9%
35%-49.9%
50%-69.9%
70%-84.9%		 -
-
-
-		 0.6m
0.6m
0.6m
0.6m		  
3 MERV 9
MERV 10
MERV 11
MERV 12		 -
-
-
-		 Less than 50%
50%-64.9%
65%-79.9%
80%-89.9%		 85% or greater
85% or greater
85% or greater
85% or greater		 -
-
-
-		 1.0m
1.0m
1.0m
1.0m		  
4 MERV 13
MERV 14
MERV 15
MERV 16		 Less than 75%
75%-84.9%
85%-94.9%
95% or greater
 90% or greater
90% or greater
90% or greater
90% or greater		 90% or greater
90% or greater
90% or greater
90% or greater		 -
-
-
-		 1.4m
1.4m
1.4m
1.4m		  
source: www.pureairsystems.com

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