FACTORIES AND INDUSTRIAL UNDERTAKINGS (WORK IN COMPRESSED AIR) REGULATIONS - SCHEDULE 3 DECOMPRESSION PROCEDURE (Regulation 11 (1))

Hong Kong Regulations

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FACTORIES AND INDUSTRIAL UNDERTAKINGS (WORK IN COMPRESSED AIR) REGULATIONS - SCHEDULE 3

DECOMPRESSION PROCEDURE (Regulation 11 (1))

[regulations 3, 8, 11 (1),
16 & 17]

PART I

General

1. The decompression of persons who have been employed in compressed air at a pressure exceeding 14 pounds per square inch shall be according to the Decompression Tables in this Schedule.

2. For the purposes of this Schedule-
"basic pressure" (基本氣壓) means the highest pressure at which a person has been employed in compressed air during a working period;
"working period" (工作時間) means the period, or the sum of the periods, during which, since last subject to ordinary atmospheric pressure for not less than 12 hours, a person is exposed to pressure.

PART II

Normal Decompression

3. Except where decanting under Part III is carried out, the procedure for the decompression of a single person, or 2 or more persons whose working periods and basic pressures fall within the same range, shall be as follows-

(1) Before the decompression is commenced, the lock attendant shall ascertain that the recording pressure gauge is in good working order and correctly zeroed.

(2) The working period and basic pressure of such person or persons, as the case may be, shall be ascertained in order to determine which Decompression Table shall apply.

(3) The pressure shall be reduced at the rate of approximately 5 pounds per square inch per minute to, but not lower than, the first stage according to the appropriate Decompression Table.

(4) The pressure under sub-paragraph (3) shall be maintained for the number of minutes prescribed in the Decompression Table.

(5) The pressure maintained under sub-paragraph (4) shall then be reduced at the rate of approximately 5 pounds per square inch per minute to the next stage of the Decompression Table.

(6) The procedure in sub-paragraphs (4) and (5) shall be followed until decompression is completed.

(7) If an automatic apparatus is used to control the decompression, the lock attendant shall ensure that the decompression procedure is accurate. If the automatic apparatus fails in any way, the lock attendant shall control the decompression manually according to the procedure in this paragraph and shall inform the person appointed under regulation 5(1).

4. When 2 or more persons, whose working periods or basic pressures do not fall within the same range, are being decompressed in the man-lock, the procedure for decompression shall be that prescribed in paragraph 3 except that for the purposes of sub-paragraph (2) of that paragraph the longest working period and the highest basic pressure of any one of such persons shall be taken for the application of the appropriate Decompression Table.

5. Where a person in a man-lock collapses or is taken ill during decompression, the lock attendant in charge shall raise the pressure in the man-lock to the pressure in the working chamber and shall report the matter immediately to the medical lock attendant on duty. The lock attendant shall then follow the instructions of the medical lock attendant or the appointed medical practitioner on duty. (80 of 1997 s. 102)

PART III

Decanting

6. The procedure for the decanting of persons shall be as follows-

(1) The persons shall be decompressed in the man-lock rapidly but at a speed that does not cause than discomfort.

(2) The persons shall then be transferred to the decant lock.

(3) The person shall be recompressed to a pressure of 1 pound per square inch above the basic pressure.

(4) The pressure under sub-paragraph (3) shall be maintained for 5 minutes.

(5) Decompression shall then be carried out according to the appropriate Decompression Table based on the pressure under sub-paragraph (3).

7. The rate of recompression in the decant lock may be at a speed faster than that recommended for normal compression but at a speed that does not cause discomfort to the persons in the lock.

8. If during recompression in the decant lock a person develops 'ear block', compression shall be stopped. If the affected person cannot clear his ears within 3 minutes, the decant lock shall be reduced to atmospheric pressure and that person shall be removed from the decant lock. The remaining persons in the decant lock shall be recompressed immediately. The affected person shall be transferred rapidly back to the man-lock where he shall be given a careful recompression followed by the requisite decompression. If the man-lock is not available, the procedure shall be carried out in the medical lock. In any event, the medical lock attendant shall be informed at the first possible opportunity.

DECOMPRESSION TABLES

TABLE 1

WHERE THE WORKING PERIOD IS NOT OVER 1/2 HOUR

Basic pressure (Pounds per square inch)	Stage pressure (Pounds per square inch) (see Note 2)							Total time- (minutes) (See Note 3)
Basic pressure (Pounds per square inch)	28	24	20	16	12	8	4	Total time- (minutes) (See Note 3)
14 to 16								~~-----~~
16 to 18								~~-----~~
18 to 20								~~-----~~
20 to 22								~~-----~~
22 to 24								~~-----~~
24 to 26								~~-----~~
26 to 28								~~-----~~
28 to 30								~~-----~~
30 to 32							5	5
32 to 34							5	5
34 to 36							5	5
36 to 38							5	5
38 to 40							5	5
40 to 42							10	10
42 to 44							10	10
44 to 46							15	15
46 to 48						5	10	15
48 to 50						5	15	20

Notes:
1. Decompress at a rate not faster than 5 pounds per square inch per minute.
2. Decompress between stages at a rate of 5 pounds per square inch per minute.
3. Not including time between stages.
4. Where alternative decompression procedures are given (e.g. 46 pounds per square inch) the longer decompression procedure should always be chosen.

TABLE 2

WHERE THE WORKING PERIOD IS OVER 1/2 HOUR BUT UP TO
AND INCLUDING 1 HOUR

Basic pressure (Pounds per square inch)	Stage pressure (Pounds per square inch) (see Note 2)							Total time- (minutes) (See Note 3)
Basic pressure (Pounds per square inch)	28	24	20	16	12	8	4	Total time- (minutes) (See Note 3)
14 to 16								~~-----~~
16 to 18								~~-----~~
18 to 20								~~-----~~
20 to 22								~~-----~~
22 to 24							5	5
24 to 26							5	5
26 to 28							10	10
28 to 30							15	15
30 to 32							20	20
32 to 34						5	20	25
34 to 36						5	30	35
36 to 38						5	35	40
38 to 40						10	40	50
40 to 42						10	45	55
42 to 44					5	10	50	65
44 to 46					5	15	50	70
46 to 48					5	20	50	75
48 to 50					5	25	55	85

TABLE 3

WHERE THE WORKING PERIOD OVER 1 HOUR BUT UP TO AND
INCLUDING 1 1/2 HOURS

Maximum working pressure (Pounds per square inch)	Stage pressure (Pounds per square inch) (see Note 2)							Total time- (minutes) (See Note 3)
Maximum working pressure (Pounds per square inch)	28	24	20	16	12	8	4	Total time- (minutes) (See Note 3)
14 to 16							2	2
16 to 18							2	2
18 to 20							5	5
20 to 22							10	10
22 to 24							15	15
24 to 26							25	25
26 to 28						5	30	35
28 to 30						5	40	45
30 to 32						10	45	55
32 to 34						15	50	65
34 to 36						20	55	75
36 to 38					5	20	60	85
38 to 40					5	30	60	95
40 to 42					10	35	60	105
42 to 44					15	40	60	115
44 to 46				5	20	40	60	125
46 to 48				5	25	45	60	135
48 to 50				5	30	50	60	145

TABLE 4

WHERE THE WORKING PERIOD IS OVER 1 1/2 HOURS BUT UP TO
AND INCLUDING 2 HOURS

Maximum working pressure (Pounds per square inch)	Stage pressure (Pounds per square inch) (see Note 2)							Total time- (minutes) (See Note 3)
Maximum working pressure (Pounds per square inch)	28	24	20	16	12	8	4	Total time- (minutes) (See Note 3)
14 to 16							2	2
16 to 18							5	5
18 to 20							10	10
20 to 22							20	20
22 to 24							30	30
24 to 26						5	40	45
26 to 28						5	50	55
28 to 30						15	50	65
30 to 32						25	50	75
32 to 34					5	25	60	90
34 to 36					5	35	60	100
36 to 38					10	40	60	110
38 to 40					15	45	60	120
40 to 42				5	20	45	60	130
42 to 44				5	25	50	60	140
44 to 46				10	30	50	60	150
46 to 48			5	10	35	50	60	160
48 to 50			5	15	40	50	60	170

Notes:
1. Decompress at a rate not faster than 5 pounds per square inch per minute.
2. Decompress between stages at a rate of 5 pounds per square inch per minute.
3. Not including time between stages.
4. Where alternative decompression procedures are given (e.g. 46, pounds per square inch) the longer decompression procedure should always be chosen.

TABLE 5

WHERE THE WORKING PERIOD IS OVER 2 HOURS BUT UP To
AND INCLUDING 2 1/2 HOURS

Maximum working pressure (Pounds per square inch)	Stage pressure (Pounds per square inch) (see Note 2)							Total time- (minutes) (See Note 3)
Maximum working pressure (Pounds per square inch)	28	24	20	16	12	8	4	Total time- (minutes) (See Note 3)
14 to 16							5	5
16 to 18							10	10
18 to 20							20	20
20 to 22							30	30
22 to 24						5	40	45
24 to 26						10	45	55
26 to 28						15	55	70
28 to 30						20	60	80
30 to 32					5	30	60	95
32 to 34					10	35	60	105
34 to 36					15	40	60	115
36 to 38				5	15	45	60	125
38 to 40				5	25	45	60	135
40 to 42				10	30	45	60	145
42 to 44				15	35	45	60	155
44 to 46			5	15	35	50	60	165
46 to 48			5	25	35	50	60	175
48 to 50			10	25	40	50	60	185

TABLE 6

WHERE THE WORKING PERIOD IS OVER 2 1/2 HOURS BUT UP TO
AND INCLUDING 3 HOURS

Maximum working pressure (Pounds per square inch)	Stage pressure (Pounds per square inch) (see Note 2)							Total time- (minutes) (See Note 3)
Maximum working pressure (Pounds per square inch)	28	24	20	16	12	8	4	Total time- (minutes) (See Note 3)
14 to 16							5	5
16 to 18							15	15
18 to 20							25	25
20 to 22							40	40
22 to 24						5	50	55
24 to 26						15	60	65
26 to 28						20	60	80
28 to 30					5	30	60	95
30 to 32					10	35	60	105
32 to 34					15	40	60	115
34 to 36				5	20	40	60	125
36 to 38				5	25	45	60	135
38 to 40				10	30	45	60	145
40 to 42				15	35	45	60	155
42 to 44			5	20	35	50	60	170
44 to 46			10	20	40	50	60	180
46 to 48			15	25	40	50	60	190
48 to 50		5	15	30	40	50	60	200

Notes:
1. Decompress at a rate not faster than 5 pounds per square inch per minute.
2. Decomp