This standard specifies the technical requirements for decompression of diving (air diving) using compressed air as the breathing medium. This standard applies to the selection of decompression solutions for air diving within a diving depth of 60m, and also applies to the selection of decompression solutions after exposure to compressed air in a pressurized chamber. GB 12521-1990 Technical requirements for air diving decompression GB12521-1990 Standard download and decompression password: www.bzxz.net

National Standard of the People's Republic of China
Technical requirements for air diving decompression1
Air diving) decompression technical requirements. GB12521-90
This standard applies to the selection of decompression solutions for air diving within a diving depth of 60m, and also applies to the selection of decompression solutions after exposure to compressed air in a pressurized chamber.
2 Terms
2.1 Diving depth divingdepth
The maximum depth reached by the diver during diving, measured in meters (m) of the height of the sea water column. When a diver is exposed to compressed air in a pressurized chamber, the pressure is equivalent to the height of the sea water column as the diving depth. 2.2 Underwater working time bottomtime
The period of time from when the diver enters the water to when the diver completes the diving operation and begins to ascend, measured in minutes (min). 2.3 Decompression
The process in which a diver gradually returns to the surface or normal pressure according to prescribed procedures and requirements after being exposed to compressed air during air diving or a pressurized chamber. 2.3.1 Underwater stage decompression: The decompression process of a diver in the water is divided into rising, staying, rising again, staying again, until returning to the surface, when the decompression ends, it is called underwater stage decompression. When implementing underwater stage decompression, the breathing medium can be compressed air or medical oxygen. 2.3.2 Surface decompression: Most or all of the diver's decompression process is performed in the surface pressurization chamber after leaving the water, which is called surface decompression. When implementing water surface decompression, the breathing medium can be compressed air or medical oxygen. 2.4 The decompression schedule decompression schedule specifies the decompression steps and schedule according to the combination of diving depth and underwater working time. 2.4.1 Basic decompression schedule is a decompression schedule selected based on the diver’s actual diving depth and underwater working time as the basic parameters. 2.4.2 Extended decompression plan modified decompression schedule When the outside world or/and the diver himself has some or some factors that are not conducive to safe decompression, the decompression plan needs to be extended on the basis of the basic plan. At this time, the decompression plan is The plan is called extended decompression plan, 2.5 stop decompressionstop
In order to gradually discharge the high-tension nitrogen from the body during decompression, the diver must stay at the specified depth for a certain time, and the specified stop depth is called a stop.
2.6 First stop firststop
The stop with the largest depth specified in a decompression plan is called the first stop. 2.7 Time to first stop: The time from the completion of the diving operation to the time the diver reaches the first stop, measured in minutes (min). The State Bureau of Technical Supervision approved the implementation on 1991-08-01 on 1990-12-03
2.8 stoppage time
GB12521-90
When a diver decompresses, he arrives at a stop station and leaves the station. Stop time. Measured in minutes (min). 2.9 The total decompression time totaltimefordecomptession is the sum of the time to rise to the first stop, the stay time at each stop, the 1-min transition time between each stop, and the 1-min time to rise from the 3m station back to the water surface.
2.10 Suitable diving time limit limitingline In order to ensure the safety and health of divers, the decompression table stipulates the underwater working time limit that should not be exceeded for different diving depths. 2.11 Surface interval time surfaceintermittenttime is the sum of the time it takes for a diver to rise from the last stop in the water, return to the surface, unload, and enter the pressurization chamber to pressurize to a predetermined pressure when performing surface decompression, measured in minutes (min). 2.12 Repeated diving repetitivedive
A dive performed within 12 hours after a dive. 2.13 Residual Nitrogen Time When selecting a repeated diving decompression plan, a time amount expressed in minutes (min) needs to be added to the underwater working time of repeated diving to represent a certain amount of remaining nitrogen in the diver’s body after the last dive decompression. To measure the influence of nitrogen, this time is called the remaining nitrogen time. 2.14 Surface interval time surfaceintervaltime is the time from the end of the last dive decompression to the start of repeated dives. 3 Technical requirements for air diving decompression
Select the decompression plan according to the following classification requirements and the air diving decompression table (see Appendix A (reference part) for instructions). Air diving decompression table
diving
depth
m
12
15
18
underwater work| |tt||Working time
min
360
105
145
180
240
300|| tt||45
60
80
105
145
180
240
rose to No.|| tt||Time of one stop

min
2
2
2
2
2| |tt||2
3
2
2
2
2
2
2||tt ||36
a
Stop depth, m
21
Dwell time, min
3
10||tt| |3
8
9
18
10
14
15
16
5
1
16
20
26
23
Decompression
Total time
min
2
2
13
17
22
30
3
80|| tt||17
23
32
38
51
Repeated Dive
Water Retrieval
Symbol|| tt||M
M
o
z
*
H
K
L||tt| |N
Z
z
diving
depth
21
24
27
30
Underwater work
Working time
min
35
45
60
80
105
145
180
240
25
35
45
60
80| |tt||105
145
180
240
20
25
35
45||tt ||60
80
105
145
180
15
20
25
35
46
60
80
105
145
180
rose to No.
Time of one stop

min
3
3
3
2
2||tt| |2
2
2
3
3
3
3
2
2
2
2
2
3
3
3
3|| tt||2
2
2
4
4
4
3
3||tt| |3
2
2
2
2
36
33
30
GB12521 —90
continuation table
stop depth, m
27
24
21
18
15| |tt||Dwell time, min
4
4
2
9
12
2
5
10
14
13
19
12
3
10
9|| tt||13
19
11
12
16
1
10
14||tt| |15
21
9
7
8
12
18
7
10
12
18
19
7
9
15
21
25|| tt||2
10
14
18
25
30
6
8||tt| |11
14
19
3
5
17
17
21
29
31
24
36
6
6
10
10
18|| tt||23
28
32
12
12
20
22
28||tt| |33
5
13
15
22
28
36
40
20
24
25
27
34
39
50
2
12|| tt||22
23
24
29Www.bzxZ.net
43
51
1
4||tt| |15
23
25
28
39
52
61
Free download of various US standard industry materials Decompression
Total time
min
3
9
21
29
44
56
71
94
3
10
31
39
47
60| |tt||84
109
141
4
6
16
39
48||tt ||59
86
120
144
4
6
9
25
44
58
83
111
159
193
Repeated dive
Water retrieval
Symbol
G
K
L
M
o
z
z
*| |tt||F
K
K
L
N
o
z
*||tt ||*
F
J
J
L
M
N
z
*
*
E
1
1
K
N
0
*
*
|tt||水下工
作时间
min
15
20
25
35
45
60
80
105
145
180
10
15
20|| tt||25
35
45
60
80
105
145
10||tt| |15
20
25
35
45
60
80
105
145
10
15
25
25
35
45
60
80|| tt||105
145
最好到第
一工业站
最术
min
5
4
4
3
3
3
8
2
2
2| |tt||5
5
5
4
4
3
3
3||tt ||3
2
6
5
5
4
4
4
3
2
2
2
6
6
5
5
4| |tt||4
3
3
3
2
36
33
30||tt ||GB1252190
绝表
混合站站站，m
27
8
12
24
21
18
混合时间，min
8
9
16
7
13
11
5
6
13
14
10
16
2
12| |tt||15
18
13
19
4
11
15
4||tt ||10
14
18
9
14
18
19
15
6
12
15
22
4
10
14
17
10| |tt||14
18
20
4
16
17
20
26||tt ||12
12
12
19
20
24
5
14
18
19
24
3
6
18
20
21
30| |tt||9
10
20
22
23
39
5
8||tt ||14
16
20
30
39
2
10
12
16
21
24
37
6
12
16
22
23| |tt||31
44
9
14
19
23
25
34||tt ||49
6
10
14
17
25
33
42
60
6
12
13
18
27
37
48
10| |tt||16
20
24
28
47
59
4
14||tt ||17
22
26
32
53
75
3
3
10
16
24
26
32
41
65
73
3| |tt||4
12
17
24
30
35
47
72||tt ||6
9
14
18
27
30
38
57
85
9
15
16
22
27
32
42
76| |tt||105
凯去
总时间
min
5
8
15
37| |tt||52
76
99
141
203
262
5
9||tt ||10
27
46
66
90
124
169
247
6
12
15
37
57
77
117
147
214| |tt||304
6
16
26
47
70
91
138||tt ||174
249
368
电影潜
水电影
symbols
F
1||tt ||I
K
L
N
0
*
*
*
D
H
H
1
L
N
0
*
*| |tt||E
F
H
J
N
0
z
*||tt ||*
*
E
G
J
N
*
*
*
*
工
作时间
min
10
15
20
25
35
45
60
80
105
145
5
10
15
20|| tt||25
35
45
60
80
105
145
5
10
15
20||tt| |25
35
45
60
80
105
民动到第
一工业站|| tt||time
min
6
6
6
5
5
4||tt ||3
3
3
2
7
6
6
6
5
5
4
3
3
3
3
7
7| |tt||6
6
6
5
4
3
3
3||tt ||36
33
12
11
13
12
14
12
13.时间，min
11
14
12
15
1
11
14
16
10
14
14
14
16
8
13
15| |tt||17
12
15
15
15
16
19
12||tt ||16
17
19
10
14
18
19
13
16
18
20
12
16
19
20
22
13| |tt||17
21
22
15
10
17
18
21||tt ||32
6
15
18
21
26
40
12
14
21
24
29
12
3
11
17
20| |tt||19
28
48
6
15
19
21
23||tt ||33
56
5
10
19
22
24
29
38
9
16
22
24
25
39
59
4| |tt||10
18
23
26
38
45
72
8||tt ||13
20
27
35
49
56
6
15
20
25
30
38
61
86
3
16
22| |tt||26
37
49
70
90
9
12
18||tt ||24
30
39
57
80
3
12
16
18
23
29
37
52
79
113
2
12| |tt||17
20
29
33
44
66
94
136||tt ||5
14
18
21
31
39
49
77
111. |54
79
112
162
208
300
433
7
9
23
37
61
100
143
195
268
359|| tt||508
7
13
31
53
72
116
166||tt| |233
329
422
电影潜
水电影
symbols
c
G||tt| |H
N
0
*
*
*
*
D
F
H
J
K
N
*
*
*
*|| tt||*
D
F
H
J
L
*
*||tt| |*
*
+

水下工
作时间
min
5
10
15
20
25
35
45
60
80
105
5
10
15| |tt||20
25
35
45
60
80
5
10||tt ||15
20
25
35
45
60
80
是以到第||tt ||一电影站
time
min
8
7
7
6
6|| tt||5
4
4
3
3
8
7
7||tt| |6
5
5
4
4
3
9
8
7
6
6
5
5
4
4
36
12|| tt||13
33
12
13
14
12
15
30||tt| |6
13
14
12
15
14
16
GB12521—90||tt| |结表
最作站 depth of depth，m
27
12
16
14
7
14
17
12| |tt||16
17
24
8
14
17
16
12||tt ||21
18
混合时间，min
11
12
16
20
21|| tt||8
14
16
18
14
16
19
18||tt| |23
12
18
20
26
17
20
24
26
13
18
21
28
4
15
20
24|| tt||32
15
14
19
23
29
32
9||tt| |15
21
27
34
10
16
24
29
39
12
11
17
22
27
35
42
10|| tt||12
18
26
32
42
10
14
19||tt| |29
36
49
10
13
21
31
37
58
62
12
24
35
45
64
7
13|| tt||16
28
39
49
70
10
14
19||tt| |29
37
48
64
92
11
16
20
34
44
79
3
12
15
22
40
48|| tt||69
90
7
17
18
22
39
47||tt| |65
84
124
10
18
19
24
43
56
72
93
11
19
20
24
52
60|| hr||80||hr||105||hr|| tt||59
80
142
205
282
386
483
8||tt| |20
43
67
89
167
246
326
441
9
24
48
73
102
194
278
380
507|| tt||电影潜
水电影
symbols
D
F
1
*
*|| tt||*
*
*
*
D
G
1
*||tt| |*
*
*
*
*
E
1
*
*
*
*
*
*
*
3.1 电影的凯去图像可来用电影水水下电影凯去或歈气水下电影电影, some programs can also use air water face pressure reduction 或oxy气水额 pressure reduction, and it may be necessary to convert from one type of pressure reduction method to another pressure reduction method. 3.2 3.3 When taking a basic pressure reduction plan, if diving The depth is the same as the depth of a certain depth. The situation of the program, should be selected more basic pressure reduction program underwater working time next, second stage or diving depth 。3.5 When using air depressurization, the stop time of each stop station is set according to the number on the table；后再取半数。后再有半数。很气击去电影电影吻水30min问是加5min间歯呼吸水水。
GB12521—90
3.6后去到9m來间（含9m）下载后气水下数Decompression. When the oxygen pressure reduction stage is implemented, the 12m stopover station can be connected to the oxygen gas in advance, the 12m stopover time is still according to the prescribed time of the air pressure reduction stage, the 9m stopover station must be connected to the oxygen pressure reduction. necessary时代么9m最了站或6m最乐站免方法最了电影应时时间的最好的最佳教，then用3min slowly rise to return to water surface。
3.7 Divemen员在水下在水下最好下载可以法小最佳在线在线3.8 When the water surface is reduced, the divers cannot continue to carry out the water in the stage when the pressure is reduced.
3.9 Diving depth within 45m (including 45m) ), 水下下载时间在水下定宜时间在水下官宜时间在水下官宜时间分在水下安家时间分内容发水水面去在最好可以可以可可去合水下的水下的水下的水水上的水上的水洗3.10 The diving depth exceeds 45m or the working time exceeds the suitable diving time limit, generally不宜安全水面化式。 遇 special circumstances need to implement water surface decompression when only oxygen gas can be used to decompress the water surface. 3m各吸oxy repeated stop for 10min，then according to the original pressure reduction scheme。 Can be within 12m(含12m) of each stopover station's stopover time more often set up in 12m and 9m stopover station。 3.11古塑*的pressure reduction scheme不宜时间安全水水外，全全家去去在可间通乐水家。GB12521—90
附较A
“水水水家击去表”使用设计
(参考件）|| tt||A1 水水员在水下最作轻或中等开动最作，水水最作机水水温10℃下载、流速0.Within 5m/s, the substrate is hard, and visibility is good; divers who are healthy, feel good subjectively, regularly perform compression exercises, have certain work experience, and have no history of being susceptible to decompression sickness can use the basic decompression plan. A2 divers who are familiar with the implementation steps of surface decompression, have no history of decompression sickness, have good Eustachian tube ventilation performance, and feel good subjectively at the end of underwater work can use surface decompression. A3 If a diver accidentally rises directly from the bottom to the surface and the time spent on the surface does not exceed 5 minutes, he should dive as soon as possible to a depth 3 meters deeper than the first stop and stay for 5 minutes. At this time, the calculation of underwater working time should include this time The underwater working time of the dive, the time to rise directly to the surface, the time to delay on the surface, the time to repeat the dive and the time to stay at the depth, and select an appropriate decompression plan accordingly. If the diver has been delayed on the surface for more than 5 minutes but has no symptoms or signs of decompression sickness, he should dive to the operating depth as soon as possible and stay for 5 minutes. At this time, the method for calculating underwater working time and the principles for selecting a decompression plan are the same as above. The steps for selecting the decompression plan for A4 repeated dives are as follows: Based on a representative letter (repeated dive search symbol) of the decompression plan selected after the last dive and the surface interval time, a parameter used to retrieve the remaining nitrogen time is obtained from Table A1 representative letter (remaining nitrogen time search symbol), and then check the remaining nitrogen time that should be added to the underwater working time of repeated diving according to Table A2, and then select the decompression plan for repeated diving based on the diving depth of the repeated diving. Table AI surface interval timetable
Repeated dive search symbol
z
o
N
M
L
K
J
I
H
2
10
22
23
34| |tt||10
23
35
24
36
10
24
49||tt ||62
37
51
25
39
10
25
63
16
52
67
40
54
26
42
10
26| |tt||79
96
68
55
59
27
45
10||tt ||28
Remaining nitrogen time search symbol
91
115
85
103
90
60| |tt||78
29
49
10
31
116
104
124||tt ||113
99
t
32
94
10
L
162
125
149
114
138
100
125
72
95
55| |tt||79
34
59
10
36
163
150
179||tt ||167
126
154
98
123
80
107
60
89
37
66
191
225
180
213
168
202| |tt||155
188
14
124
158
108
140
90||tt ||122
67
101
226
269
214
257
203
244
189
232
159
201
141
184
123
164| |tt||102
143
270
322
258
316
245
303||tt ||233
289
217
275
202
259
185
242
165
223
144
200
328
317
404
304
92| |tt||290
378
276
260
348
340
224
312||tt ||201
289
min
41
605
405
594
393
583
379
568
363
552
349
538
341
520| |tt||313
501
290
606
720
595
720
584||tt ||720
569
720
553
720
539
720
521
720
502
720
480
720
A5
Repeated dive search symbol
G||tt| |F
E
D
c
B
A
Repeated dive depth
m||tt| |12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
Z|| tt||z
257
169
122
100
84
73
64||tt| |57
46
42
40
37
35
32
31
o
241
160
117
96
80
70
62
55|| tt||50
44
40
38
36
34
31
30||tt| |N
213
142
107
87
73
64
57
51
46
40
38
35
33
31
29
28|| tt||GB
1252190
continued table A1
remaining nitrogen time search symbol
H
2 remaining nitrogen schedule
table A2
G
10
40
remaining nitrogen time search symbol
M
187
124
97
80
68
58
52
47
3
38| |tt||35
32
31
29
27
26
L
161||tt ||111
88
72
53
48
42
39
35
32
30
28
26
25
24
138
99
79| |tt||64
54
47
43
38
35
3
29||tt ||27
26
24
22
21
J
116
87
70
57
48
43
38
34
32
28
26| |tt||24
23
22
20
19
101
76
61||tt ||50
43
38
34
31
28
25
23
22
20
19
18
17
H
87
66
52| |tt||43
38
33
30
27
25
22
20||tt ||19
18
17
16
15
G
73
56
44
37
32
29
26
24
21
19
18| |tt||17
16
15
14
13
F
41
75||tt ||10
45
F
61
47
36
31
28
24
22
20
18
16
15
14
13
13| |tt||12
11
E
76
119
46
89
10||tt ||54
E
49
38
30
26
23
20
18
16
12
12
11
10
10
10
D| |tt||120
178
90
148
55
117
10
69||tt ||D
37
29
24
20
18
16
14
13
12
11
10
8
8
8
c
179| |tt||265
149
237
118
202
70
158
10||tt ||90
c
25
21
17
15
13
11
10
10
6
6
6
6
min
B
266| |tt||455
238
425
203
392
159
348
100||tt ||169
10
130
A
456
720
426
720
393
720
349
720
170
720
131
720
10| |tt||720
min
B
17
13
11
S
A||tt ||7
6
S
3
3
3
2
2
2
2
2
2
凯去方法或正解加去电影。
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