NAS codes
Table 11
shows the original NAS 1638 contamination limits by maximum particle counts per 100 mL
of fluid or by the weight of contamination per 100 mL of fluid.
Table 11 NAS 1638 codes for maximum contamination limits
Class
00
0
1
2
3
4
5
6
7
8
9
10
11
12
1
Same as ARP598
SAE codes
Table 12
shows the SAE AS4059 codes and the cleanliness levels.
Table 12 SAE AS4059 cleanliness levels by particle count
Size, ISO 4402 calibration, or
optical microscope count
Size, ISO 11171 calibration, or
2
electron microscope
Size code
Class 000
Class 00
Class 0
Class 1
Class 2
Class 3
Class 4
Class 5
Class 6
26 English
5 to 15 µm
1,000
2,000
4,000
8,000
16,000
32,000
64,000
128,000
256,000
512,000
1,024,000
> 1 µm
1
> 4 µm(c)
A
195
390
780
1560
3120
6250
12,500
25,000
50,000
Particle size range
125
250
500
Maximum contamination limits (particles/100 mL)
> 5 µm
> 15 µm
> 6 µm(c)
> 14 µm(c) > 21 µm(c) > 38 µm(c) > 70 µm(c)
B
C
76
14
152
27
304
54
609
109
1220
217
2430
432
4860
864
9730
1730
19,500
3460
1
15 to 25 µm
22
44
89
178
356
712
1,425
2,850
5,700
11,400
22,800
45,600
91,200
182,400
> 25 µm
> 50 µm
D
E
3
1
5
1
10
2
20
4
39
7
76
13
152
26
306
53
612
106
> 100 µm
F
0
0
0
1
1
2
4
8
16