|
Air filter manufactures
rate their products according to standards established by the
American Society of Heating, Refrigeration, and Air Conditioning
Engineers (ASHRAE), which uses two different methods for describing
filtration efficiency Test 52.2 and Test 52.1. A third test,
referred to as a dust spot test is:
-
Standard 52.2-1999:
This system quantifies air filtration efficiency against particle
size ranges: 3 to 10 μm (micrometers or microns), 1 to 3 μm, and
0.3 to 1 μm. Particle size efficiency is further expressed based
on a Minimum Efficiency Reporting Value (MERV) between 1 and 16.
A higher MERV indicates greater filter efficiency and one that is
more effective against smaller particles. The 52.2-1999 system is
a newer approach which is more descriptive.
-
Standard 52.1-1992:
This system quantifies air filter efficiency in terms of mass
of particles removed or 'arrestance'. The 52-1 method is also
called a weight-arrestance test. Weight-arrestance tests are
misleading because they tell only how well a filter will remove
relatively large particles but not the smaller particles typically
found in dust.
A third test, which is
actually part of the 52.1 is called an 'atmospheric-dust-spot
test'. A dust-spot test is more useful than weight arrestance
because it measures a filter's ability to capture particles within a
given range, usually between 0.3 and 6 μm.
Comparison of the 52.2 (MERV) and 52.1
Rating Systems
|
ASHRAE 52.2 |
ASHRAE 52.1
|
|
MERV
|
3 - 10 µm
|
1 - 3 µm
|
0.3 - 1 µm
|
Arrestance
|
Dust Spot
|
Dust spot |
|
1
|
<20%
|
-
|
-
|
<65%
|
<20%
|
>10
µm
|
|
2
|
<20%
|
-
|
-
|
65-70%
|
<20%
|
|
3
|
<20%
|
-
|
-
|
70-75%
|
<20%
|
|
4
|
<20%
|
-
|
-
|
>75%
|
<20%
|
|
5
|
20-35%
|
-
|
-
|
80-85%
|
<20%
|
3.0-10
µm |
|
6
|
35-50%
|
-
|
-
|
>90%
|
<20%
|
|
7
|
50-70%
|
-
|
-
|
>90%
|
20-25%
|
|
8
|
>70%
|
-
|
-
|
>95%
|
25-30%
|
|
9
|
>85%
|
<50%
|
-
|
>95%
|
40-45%
|
1.0-3.0
µm |
|
10
|
>85%
|
50-65%
|
-
|
>95%
|
50-55%
|
|
11
|
>85%
|
65-80%
|
-
|
>98%
|
60-65%
|
|
12
|
>90%
|
>80%
|
-
|
>98%
|
70-75%
|
|
13
|
>90%
|
>90%
|
<75%
|
>98%
|
80-90%
|
0.3-1.0
µm |
|
14
|
>90%
|
>90%
|
75-85%
|
>98%
|
90-95%
|
|
15
|
>90%
|
>90%
|
85-95%
|
>98%
|
~95%
|
|
16 |
>95%
|
>95%
|
>95%
|
>98%
|
>95%
|
|
17* |
>99%
|
>99%
|
>99%
|
-
|
>99%
|
0.3-1.0
µm
|
|
18* |
>99%
|
>99%
|
>99%
|
-
|
>99%
|
|
19* |
>99%
|
>99%
|
>99%
|
-
|
>99%
|
|
20*
|
>99%
|
>99%
|
>99%
|
-
|
>99%
|
Filter Applications
|
MERV |
Application |
|
1-4 |
minimum residential, minimum
commercial, equipment protection |
|
5-8 |
commercial, industrial, better
residential, paint booth, finishing |
|
9-12 |
better commercial, better
industrial, superior residential |
|
13-16 |
health care, general surgery,
superior commercial, smoke removal |
|
17-20* |
clean rooms, high risk surgery,
hazardous materials |
* = reserved for future
classifications |
|
|
