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 Table 8-13
Effectiveness of Non-Solid Shielding Materials Against High Impedance Waves (8-3)
FORM
Nominal Effectiveness
Open
Air-Flow Static
General
Detailed
Material
Thickness
Area
(14 kHz to 1000 MHz)
Pressure
(mils)
(inches of water)
(dB)
%
400 cu ft/min
200 cu ft/min
0.06
3
.26
1/4-inch cell,
>90
Hexcell
Al
1 inch thick
9-mil holes,
TV Shadow
>2
12
>90
28-mil centers
Mask
95% Cu
0.2
0.4
50
(Photo-
5%
0.2
50
0.5
>90
Etched)
100%
0.4
1.7
>90
36
40 count
Cu-Ni
Lektromesh
0.2
0.5
78
49
25 count
0.2
0.5
78
57
40 count
Cu
0.2
0.4
56
25 count
1/8-inch dia,
Steel
Perforated
0.27
>0.6
58
60
3/16-inch
Steel
Sheet
1/4-inch dia,
48
46
60
5/16-inch
Al
centers
7/16-inch dia,
35
37
45
5/8-inch
centers
55
36
20 (dia)
No. 16
Al
Mesh
16
x 16/sq in.
(Screen-
65 (14 kHz to 60 MHz)
No.
22
Cu
ing)
50
50
20 (dia)
No.
12
45 (14 kHz to 60 MHz)
No.
16
Bronze
No.
10
Monel
18 (dia)
40
No.
4
Galva-
30 (dia)
35
76
nized
Steel
28 (14 kHz to 40 MHz)
24
No. 2
88
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