"MERV" Rating.
means

Minimum Efficiency Reporting Value
see chart below

Group Number

 'MERV' Rating

E3 E3 E3

Average  Arrestance
(ASHRAE 52.1)

Minimum
Final Resistance
(In. W.G.)

Average Particles
Size Efficiency (PSE)
0.3 - 1.0 Microns

Average Particles
Size Efficiency (PSE)
1.0 - 3.0 Microns

Average Particles
Size Efficiency (PSE)
3.0 - 10.0 Microns

1 1
2
3
4
-
-
-
-
-
-
-
-
Less than 20%
Less than 20%
Less than 20%
Less than 20%
Less than 65%
65% - 69.9%
70% - 74.9%
75% or Greater
0.3"
0.3"
0.3"
0.3"
2 5
6
7
8
-
-
-
-
-
-
-
-
20% - 34.9%
35% - 49.9%
50% - 69.9%
70% - 84.9%
-
-
-
-
0.6"
0.6"
0.6"
0.6"
3 9
10
11
12
-
-
-
-
Less than 50%
50% - 64.9%
65% - 79.9%
80% - 89.9%
85% or Greater
85% or Greater
85% or Greater
90% or Greater
-
-
-
-
1.0"
1.0"
1.0"
1.0"
4 13
14
15
16
Less than 75%
75% - 84.9%
85% - 94.9%
95% or Greater
90% or Greater
90% or Greater
90% or Greater
95% or Greater
90% or Greater
90% or Greater
90% or Greater
95% or Greater
-
-
-
-
1.4"
1.4"
1.4"
1.4"

 Notes:
          1) Ashrae Standard 52.2 tests are to be conducted at one of (7)
              seven air flow rates.

              118 FPM - (0.60 m/s)              492 FPM - (2.50 m/s)
              246 FPM - (1.25 m/s)              630 FPM - (3.20 m/s)
              295 FPM - (1.50 m/s)              748 FPM - (3.80 m/s)
              374 FPM - (1.90 m/s)

 

      2) The air flow rate at which the filter was tested is  
          included in the MERV Rating (10 @ 2.50 m/s)
      3) Filter with efficiency of less than 20% (MERV-1
          through MERV-4) must also be tested for
          arrestance per ASHRAE Standard 52.1
      4) Final resistance must be at least twice the
          intial resistance at the test air flow rate or the
          values shown in the table above or whichever
          is greater. 

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