Handbook of air conditioning and refrigeration / Shan K

15.64 CHAPTER FIFTEEN
Test Unit
Fan
HEPA
filter
Aerosol
injection
Dust
feed
FIGURE 15.36 ANSI/ASHRAE Standard 52.2 specified air filter test unit.
Sample
probe
Test air
filter Nozzle
Sample
probe
HEPA
filter
● The test method uses laboratory-generated potassium chloride dispersed into the airstream as the
test aerosol.
● Air filters are classified according to their minimum efficiency report value (MERV) into five
categories: coarse, low, medium, high, and ultrahigh efficiency.
The weight arrestance test method to assess coarse filters, the new particle size method to assess
low-, medium- and high-efficiency filters and DOP method for filters used in clean rooms and clean
spaces. Table 15.3 lists MERV for air filters.
The performance of an air filter is tested in a test unit. Figure 15.36 shows an air filter test unit
specified by ANSI/ASHRAE Standard 52.2-1999. The test unit consists of a blow-through fan, a
test duct, a tested filter, two samplers, a particle counter, a flow nozzle, two sets of Pitot tubes and
TABLE 15.3 Minimum Efficiency Reporting Value (MERV) Parameters
Standard 52.2
minimum
efficiency
reporting value
Composite average particle size efficiency, %
in size range, �m
Range 1 Range 2 Range 3
Average
arrestance, %
by Standard 52.1
Minimum final resistance
(MERV) 0.30–1.0 1.0–3.0 3.0–10.0 method Pa in. of water
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
E1 � 75
75 � E1 � 85
85 � E1 � 95
95 � E1 n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
E2 � 50
50 � E2 � 65
65 � E2 � 80
80 � E2 90 � E2 90 � E2 90 � E2 95 � E2 E3 � 20
E3 � 20
E3 � 20
E3 � 20
20 � E3 � 35
35 � E3 � 50
50 � E3 � 70
70 � E3 85 � E3 85 � E3 85 � E3 90 � E3 90 � E3 90 � E3 90 � E3 95 � E3 Aavg � 65
65 � Aavg � 70
70 � Aavg � 75
75 � Aavg n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
75
75
75
75
150
150
150
150
250
250
250
250
350
350
350
350
0.3
0.3
0.3
0.3
0.6
0.6
0.6
0.6
1.0
1.0
1.0
1.0
1.4
1.4
1.4
1.4
Note: The minimum final resistance shall be at least twice the initial resistance, or as specified above, whichever is greater.
Source: ANSI/ASHRAE Standard 52.2–1999. Reprinted with permission.